dive 8 planning - san francisco state university

SECTION PAGE

8.0 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 18.1 DIVE PLANNING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 1

8.1.1 Selection of Diving Equipment . . . . . . . . . . . . . . . . . . . . . . 8- 28.2 DIVE TEAM ORGANIZATION . . . . . . . . . . . . . . . . . . . . . . . . 8- 2

8.2.1 Divemaster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 28.2.2 Diving Medical Officer/

Diving Medical Technician . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.2.3 Science Coordinator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.2.4 Divers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.2.5 Support Divers and Other

Support Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 38.3 ENVIRONMENTAL CONDITIONS . . . . . . . . . . . . . . . . . . . . . 8- 3

8.3.1 Surface Environmental Conditions . . . . . . . . . . . . . . . . . . . 8- 38.3.2 Underwater Environmental

Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 48.4 DIVING SIGNALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 8

8.4.1 Hand Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 88.4.2 Surface-to-Diver Recall Signals . . . . . . . . . . . . . . . . . . . . . 8-118.4.3 Line Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-118.4.4 Surface Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11

8.5 AIR CONSUMPTION RATES . . . . . . . . . . . . . . . . . . . . . . . . . . 8-118.5.1 Determining Individual Air

Utilization Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-148.5.2 Scuba Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-148.5.3 Scuba Air Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-168.5.4 Surface-Supplied Air Requirements. . . . . . . . . . . . . . . . . . . 8-17

8DivePlanning

8.0 GENERALDiving with air as the breathing gas is conducted

using a variety of life-support equipment. The most fre-quently used mode is open-circuit scuba, where the divercarries the compressed air supply. Divers can also useumbilical-supplied air with a scuba regulator, and either afull-face mask or a lightweight diving helmet. This sectiondeals with planning for air dives, operational methods ofcalculating air supply requirements, personnel require-ments, and environmental conditions.

8.1 DIVE PLANNINGCareful and thorough planning are the keys to con-

ducting an efficient diving operation and are imperativefor diver safety as well. The nature of each dive operationdetermines the scope of the planning required. The diveplan should take into account the ability of the least quali-fied diver on the team and be flexible enough to allow fordelays and unforeseen problems. It should include at leastthe following:

• Definition of Objectives– A clear statement of the purpose and goals of the

operation• Analysis of Pertinent Data

– Surface conditions, such as sea state, air tempera-ture, and wind chill factor

– Underwater conditions, including water tempera-ture, depth, type of bottom, tides and currents,visibility, extent of pollution, and hazards

– Assistance and emergency information, includinglocation, status, and contact procedures for thenearest recompression chamber, air evacuationteam, U.S. Coast Guard, and nearest hospital

• Diving Team Selection– Divemaster– Medical personnel– Tenders/timekeeper – Coxswain/surface-support personnel

• Diving Mode Selection– Skin (snorkeling)

– Open-circuit scuba– Rebreathers– Surface-supplied– Hookah

• Equipment and Supplies Selection– Breathing gas, including a backup supply– Dive platform and support equipment, including

diver/crew shelter – Oxygen resuscitator and first aid kit– Backboard– Dive flag – Diving gear, tools, etc.– Water– Communications

• Schedule of Operational Tasks for All Phases– Transit to the site– Assembling dive gear and support equipment– Predive briefing– Calculating allowable/required bottom time– Recovery– Cleaning, inspection, repair, and storage of gear – Debriefing of divers and support personnel

• Final Preparations and Safety Checks– Review of dive plan, its effect, and all safety pre-

cautions– Outline diving assignments and sequence– Complete and post on-site emergency checklist– Review diver qualifications and conditions – Secure permission from command or boat captain

for dive• Briefing/Debriefing the Diving Team

– The objective and scope of the operation– Conditions in the operating area– Diving techniques and equipment to be used– Personnel assignments– Specific assignments for each diver– Anticipated hazards– Normal safety precautions– Any special considerations – Group discussion period to answer questions by

members of the diving team

8-1

8Dive Planning

8.1.1 Selection of Diving EquipmentThe selection of the proper diving equipment

depends on environmental conditions, qualifications ofdiving personnel, objectives of the operation, and divingprocedures to be used. Although most diving is per-formed at depths less than 130 ft. (39.6 m) and oftenuses open-circuit scuba, some missions can be accom-plished using only skin diving equipment. Other morecomplex assignments require surface-supplied or closed-circuit systems. Depth and duration of the dive, ques-tions about the type of work to be accomplished (heavywork, light work, silent work), temperature of thewater, velocity and nature of current, visibility, logis-tics, and the diver’s experience and capabilities all influ-ence the selection of diving equipment. Detaileddescriptions of the various types of diving equipmentare presented in Chapter 5. For planning purposes, thefollowing guidelines may be used in selecting the appro-priate diving equipment.

Breath-Hold Diving Equipment

Generally Used For:• Scientific observation and specimen collection in

shallow water in areas where more complex equip-ment is a disadvantage or is not available

• Shallow-water photography• Scouting for diving sites

Major Advantages:• Less physical work required to cover large surface

areas• Simplified logistics• Fewer medical/physiological complications

Major Disadvantages:• Extremely limited in depth and duration• Requires diver to develop breath-holding tech-

niques• Can only be used in good sea conditions

Open-Circuit Scuba

Generally Used For:• Scientific observation• Light underwater work and recovery• Sample collection• Shallow-water research• Ship inspection and light repair

Major Advantages:• Minimum support requirements• Mobility• Accessibility and economy of equipment and

breathing medium• Portability• Reliability

Major Disadvantages:• Lack of efficient voice communication• Limited depth and duration

Umbilical-Supplied Systems

Generally Used For:• Scientific investigation• Ship repair and inspection• Salvage• Long-duration scientific observation and data

gathering• Harsh environments (low visibility, strong currents,

polluted water)Major Advantages:

• Long duration• Voice communication• Protection of diver from environment

Major Disadvantages:• Limited mobility• Significant support requirements

Closed-Circuit Systems

Generally Used For:• Observations of long duration

Major Advantages:• Mixed-gas capability• No noise or bubbles• Conservation of breathing medium• Long duration

Major Disadvantages:• Complicated maintenance• Extensive training requirements• Cost of equipment

8.2 DIVE TEAM ORGANIZATION8.2.1 Divemaster

NOAA Divemasters have complete responsibility for thesafe and efficient conduct of all NOAA diving operations. Inorder to be a NOAA Divemaster, individuals must be certi-fied NOAA Working Divers, or higher, and have completedthe NOAA Divemaster training program. When no divemas-ter is present, diving should not be conducted. The divemas-ter’s responsibilities include, but are not limited to:

• Overall responsibility for the diving operation• Safe execution of all diving• Preparation of a basic plan of operation, including

evacuation and accident management plans• Liaison with other organizations• Inspection of equipment• Proper maintenance, repair, and stowage of equip-

ment• Selection, evaluation, and briefing of divers and

other personnel• Monitoring progress of the operation, and updating

requirements as necessary• Maintaining the diving log• Monitoring of decompression (when required)• Coordination of boat operations when divers are in

the water

8-2 NOAA Diving Manual

The divemaster is responsible for assigning all divers toan operation and for ensuring that their qualifications areadequate for the requirements of the dive. The divemastermust ensure that all divers are briefed thoroughly about themission and goals of the operation. Individual responsibili-ties are assigned to each diver by the divemaster. Where spe-cial tools or techniques are to be used, the divemaster mustensure that each diver is familiar with their application.

Training and proficiency dives should be made toensure safe and efficient operations. During complex opera-tions or those involving a large number of divers, divemas-ters should perform no diving, but should, instead, devotetheir efforts entirely to directing the operation.

The divemaster is in charge when divers are in thewater during diving operations. Before any change is madeto the boat’s propulsion system (e.g., change in speed,direction, etc.), the boat captain must consult with thedivemaster.

8.2.2 Diving Medical Officer/Diving Medical Technician

When it is not practical to have a qualified diving med-ical officer on site, a Diving Medical Technician trained inthe care of diving casualties shall be assigned. The DMT istrained to respond to emergency medical situations and tocommunicate effectively with a physician not at the divingsite. There are specialized courses available to train DivingMedical Technicians in the care of diving casualties.

In the event that neither a physician nor a trained tech-nician is available, the divemaster should have available thenames and phone numbers of at least three diving medicalspecialists who can be reached for advice in an emergency.Emergency consultation is available from the service centerslisted below. Referred to as a “Bends Watch,” each of theseservices is available to provide advice on the treatment ofdiving casualties:

• Divers Alert Network, Peter B. Bennett Center, 6West Colony Place, Durham, North Carolina 27705,telephone (919) 684-8111 (ask for the DivingAccident Physician)

• Navy Experimental Diving Unit, Panama City,Florida 32407, telephone (850) 234 -4351

• Brooks Air Force Base, San Antonio, Texas 78235,telephone (210) 536-3278 ( before 7:00 a.m. andafter 4:15 p.m. MST), emergency call (210) 536-3281 (Monday thru Friday between 7:00 a.m. and4:15 p.m. MST)

All diving personnel shall have access to the phonenumbers of these facilities, available at all times, especially ifthey will be diving in remote areas.

8.2.3 Science CoordinatorOn missions where diving is performed in support of

scientific programs, a chief scientist may be needed.

The chief scientist is the prime point of contact for allscientific aspects of the program, including scientificequipment, its use, calibration, and maintenance.Working with the divemaster, the chief scientist willbrief divers on specific scientific tasks to be completedand supervise the debriefing and sample or data accumu-lation after a dive.

8.2.4 DiversAlthough the divemaster is responsible for the overall

diving operation, the diver is responsible for being inproper physical condition, for checking out personalequipment before the dive, and for thoroughly under-standing the purpose and the procedures to be used for thedive. The diver is also responsible for refusing to divewhen conditions are unsafe, when not in good mental orphysical condition, or when diving would violate dictatesof their training or applicable standards.

8.2.5 Support Divers and Other Support PersonnelIn most diving operations, the number and types of

support divers depend on the size of the operation and thetype of diving equipment used. Ideally, those surface-sup-port personnel working directly with the diver also shouldbe qualified divers. Using unqualified personnel who donot understand diving techniques and terminology maycause confusion and can be dangerous. Persons not quali-fied as divers can be used when the need arises, but onlyafter they have demonstrated that they understand proce-dures to the satisfaction of the divemaster.

8.3 ENVIRONMENTAL CONDITIONSEnvironmental conditions at a dive site should be con-

sidered when planning a diving operation. Environmentalconditions can be divided into surface conditions andunderwater conditions. Surface conditions include weather,sea state, and amount of ship traffic. Underwater condi-tions include depth, bottom type, currents, water tempera-tures, and visibility. Regional and special diving conditionsare discussed in Chapter 12.

8.3.1 Surface Environmental ConditionsWhen planning a dive, weather conditions are an

important factor. Whenever possible, diving operationsshould be cancelled or delayed during bad weather.Current and historical weather data should be reviewed todetermine if conditions are acceptable and are predicted tocontinue long enough to complete the mission. Continuousmarine weather broadcasts are provided by NOAA on thefollowing frequencies depending on the local area:

162.40 MHz, 162.475 MHz, or 162.55 MHz

These broadcasts can be heard in most areas of the UnitedStates and require only the purchase of a VHF radioreceiver. Weather radios are designed to receive onlyNOAA radio broadcasts. Regular weather forecasts and

Dive Planning 8-3

special marine warnings are available any time of the day ornight. Although both receivers pick up weather signals fromapproximately the same distance, the two-way systems havethe advantage of transmission quality.

In some cases, surface weather conditions may influ-ence the selection of diving equipment. For instance, eventhough water temperature may permit the use of standardwetsuits, cold air temperature and wind may dictate that adry suit (or equivalent) should be worn when diving froman open or unheated platform.

Whenever possible, avoid or limit diving in moderateseas. Sea state limitations depend to a large degree on thetype and size of the diving platform. Diving operationsmay be conducted in rougher seas from properly mooredlarger platforms such as diving barges, ocean-going ships,or fixed structures. When using self-contained equipment,divers should avoid entering the ocean in heavy seas orsurf, as well as high, short-period swell. If bad weathersets in after a diving operation has commenced, all diversshould be recalled. Except in an emergency, divers shouldnot attempt scuba or surface-supplied diving in rough seas(see Figure 8.1 and Table 8.1).

Because many diving operations are conducted inharbors, rivers, or major shipping channels, the pres-ence of ship traffic often presents serious problems. Attimes, it may be necessary to close off the area aroundthe dive site or to limit the movement of ships in thevicinity of the dive site. Ship traffic should be consid-ered during dive planning, and a local “Notice toMariners” should be issued. Anytime diving operationsare to be conducted in the vicinity of other ships, othervessels should be notified by message or signal that div-ing is taking place. Signal flags, shapes, and lights areshown in Table 8.2.

If the dive operation is to be conducted in the middleof an active fishing ground, divers must assume that peo-ple with various levels of experience and competencewill be operating small boats in the vicinity and may notbe acquainted with the meaning of diving signals.

Take the necessary precautions to ensure that theyremain clear of the area.

Surface visibility is important. Reduced visibility mayseriously hinder or force postponement of diving opera-tions. If operations are to be conducted in a known fogbank, the diving schedule should allow for probable delayscaused by low visibility. The safety of the diver and sup-port crew is the prime consideration in determiningwhether surface visibility is adequate. For example, in lowsurface visibility conditions, a surfacing scuba diver mightnot be able to find the support craft or might be in dangerof being struck by surface traffic.

8.3.2 Underwater Environmental ConditionsDive depth is a basic consideration in the selection of

personnel, equipment, and techniques. Depth should bedetermined as accurately as possible in the planning phases,and dive duration, air requirements, and decompressionschedules should be planned accordingly.

The type of bottom affects divers ability to see andwork. Mud (silt and clay) bottoms generally are the mostlimiting because the slightest movement will stir sedimentinto suspension, restricting visibility. The diver must orienthimself so that any current will carry the suspended sedi-ment away from the work area. Also, the diver shoulddevelop a mental picture of his surroundings so that his safeascent to the surface is possible even in conditions of zerovisibility.

Sand bottoms usually present little problem because vis-ibility restrictions caused by suspended sediment are lesssevere than with mud bottoms. In addition, sandy bottomsprovide firm footing.

Coral reefs are solid but contain many sharp protru-sions. Divers should wear gloves and coveralls or a wet-suit for protection if the operation requires contact withthe coral. Learn to identify and avoid corals and othermarine organisms that might inflict injury. There’s alsothe concern of not inflicting unnecessary damage to theenvironment during the process of studying it.


FIGURE 8.1Sea States

SS6 Waves Start to Roll

SS5 Spindrift Forms

SS3 White Caps Form

Wav

e H

eigh

t ~ F

eet (

Avg

)

Dive Planning 8-5

TABLE 8.1Sea State Chart

Sea-General

SeaState Description

Wave HeightFeet

Wind

(Bea

ufor

t) W

ind

Forc

e

Des

crip

tion

Ran

ge (K

nots

)

Win

d Ve

loci

ty (K

nots

)

Ave

rage

Ave

rage

1/

10 H

ighe

st

Sign

ifica

nt R

ange

of

Perio

ds (S

econ

ds)

t (A

vera

ge P

erio

d)

I (Av

erag

e W

ave

Leng

th)

Min

imum

Fet

ch(N

autic

al M

iles)

Min

imum

Dur

atio

n(H

ours

)

Sea

Sea like a mirror U Calm Less 0 0 0 – – – – –than 1

Ripples with the 1 Light 1–3 2 0.05 0.10 up to 0.5 10 in. 5 18appearance of scales Airs 1.2 sec. min.are formed, but withoutfoam crests.

Small wavelets still, but 2 Light 4–6 5 0.18 0.37 0.4–2.8 1.4 6.7 ft. 8 39more pronounced; short Breeze min.crests have a glassyappearance, but do not break.

Large wavelets, crests 3 Gentle 7.10 8.5 0.6 1.2 0.8–5.0 2.4 20 9.8 1.7begin to break. Foam of Breeze 10 0.88 1.8 1.0–6.0 2.9 27 10 2.4glassy appearance. Perhaps scattered whitecaps.

Small waves, becoming 4 Moderate 11–16 12 1.4 2.8 1.0–7.0 3.4 40 18 3.8larger, fairly frequent white Breeze 13.5 1.8 3.7 1.4–7.6 3.9 52 24 4.8caps. 14 2.0 4.2 1.5–7.8 4.0 59 28 5.2

16 2.9 5.8 2.0–8.8 4.6 71 40 6.6

Moderate waves, taking a 5 Fresh 17–21 18 3.8 7.8 2.5–10.0 5.1 90 55 8.3more pronounced long Breeze 19 4.3 8.7 2.8–1.0.6 5.4 95 65 9.2form; many white caps 20 5.0 10 3.0–11.1 5.7 111 75 10are formed. (Chance ofsome spray.)

Large waves begin to form, 6 Strong 22–27 22 6.4 13 3.4–12.2 6.3 134 100 12the white foam crests are Breeze 24 7.9 16 3.7–13.5 6.8 160 130 14more extensive everywhere. 24.5 8.2 17 3.8–13.6 7.0 164 140 15(Probably some spray.) 26 9.6 20 4.0–14.5 7.4 188 180 17

Sea heaps up and white 7 Moderate 28–33 28 11 23 4.5–15.5 7.9 212 230 20foam from breaking waves Gale 30 14 28 4.7–16.7 8.6 250 280 23begins to be blown in streaks 30.5 14 29 4.8–17.0 8.7 258 290 24along the direction of the 32 16 33 5.0–17.5 9.1 285 340 27wind. (Spindrift begins to beseen.)

5

4

3

2

10

6


TABLE 8.1Sea State Chart (continued)

Sea-General

SeaState Description

Wave HeightFeet

Wind

(Bea

ufor

t) W

ind

Forc

e

Des

crip

tion

Ran

ge (K

nots

)

Win

d Ve

loci

ty (K

nots

)

Ave

rage

Ave

rage

1/

10 H

ighe

st

Sign

ifica

nt R

ange

of

Perio

ds (S

econ

ds)

t (A

vera

ge P

erio

d)

I (Av

erag

e W

ave

Leng

th)

Min

imum

Fet

ch(N

autic

al M

iles)

Min

imum

Dur

atio

n(H

ours

)

Sea

Moderately high waves of 8 Fresh 34–40 34 19 38 5.5–18.5 9.7 322 420 30greater length; edges of Gale 36 21 44 5.8–19.7 10.3 363 500 34crests break into spindrift. 37 23 46.7 6–20.5 10.5 376 530 37The foam is blown in well 38 25 50 6.2–20.8 10.7 392 600 38marked streaks along the 40 28 58 6.5–21.7 11.4 444 710 42direction of the wind. Sprayaffects visibility.

High waves. Dense streaks 9 Strong 41–47 42 31 64 7–23 12.0 492 830 47of foam along the direction Gale 44 36 73 7–24.2 12.5 534 960 52of the wind. Sea begins to 46 40 81 7–25 13.1 590 1110 57roll. Visibility affected.

Very high waves with long 10 Whole 48–55 48 44 90 7.5–26 13.8 650 1250 63overhanging crests. The Gale 50 49 99 7.5–27 14.3 700 1420 69resulting foam is in great 51.5 52 106 8–28.2 14.7 736 1560 73patches and is blown in 52 54 110 8–28.5 14.8 750 1610 75dense white streaks along 54 59 121 8–29.5 15.4 810 1800 81the direction of the wind.On the whole, the surface ofthe sea takes a white appear-ance. The rolling of the seabecomes heavy and shock-like. Visibility is affected.

Exceptionally high waves. 11 Storm 56–63 56 64 130 8.5–31 16.3 910 2100 88(Small and medium-sized 59.5 73 148 10–32 17.0 985 2500 101ships might be lost to view behind the waves for a long time.) The sea is completely covered with longwhite patches of foam lyingalong the direction of the wind. Everywhere the edgesof the wave crests are blowninto froth. Visibility affected.

Air filled with foam and 12 Hurricane 64–71 >64 >80 >164 10–(35) (18)spray. Sea completely whitewith driving spray; visibilityvery seriously affected.

7

8

9

Dive Planning 8-7

White

Sport Diver Flag

International Code Flag"A"

International Code Flags"I and R"

International DayShapes and Lights

Red

Red

White

Yellow

Black

BlackBall

BlackDiamond

BlackBall

Shapes/Day Lights/Night

Yellow

Red

Red

White

Red

Blue

"I"

"R"

Displayed by civilian divers in the UnitedStates. May be used with code flag alpha(flag A), but cannot be used in lieu of flag A.The Coast Guard recommends that the red-and-white diver's flag be exhibited on a floatmarking the location of the divers.

Must be displayed by all vessels operatingeither in international waters or on thenavigable waters of the United States thatare unable to exhibit three shapes (see lastrow of this table). Flag A means that themaneuverability of the vessel is restricted.

"Divers are below. Boats should notoperate within 100 feet."(Varies in accordance withindividual state laws.)

"My maneuverability is restrictedbecause I have a diver down; keep wellclear at slow speed."

"I am engaged in submarine surveywork (underwater operations); keepclear of me and go slow."

"This vessel is engaged in underwateroperations and is unable to get out of the way of approaching vessels."

Displayed by all vessels in internationaland foreign waters engaged in underwateroperations.

Displayed by all vessels in international and foreign waters.

TABLE 8.2Signal Flags, Shapes, and Lights

Signal Use Meaning


Currents must be considered when planning and exe-cuting a dive, particularly when using scuba. When a boatis anchored in a current, a buoyed safety line at least 100 ft.(30.5 m) in length should be trailed from the stern duringdiving operations. If, on entering the water, a diver is sweptaway from the boat by the current, the diver can use thissafety line to keep from being carried down current.

Free-swimming descents should be avoided in cur-rents, unless a means of retrieving the diver is available incase they miss their intended target. Descent from ananchored or fixed platform into water with currents shouldbe made via a down line. A trail line also should be usedunless a pickup boat is operating down current so thatdivers surfacing some distance from the entry point can beretrieved. A knowledge of changing tidal currents mayallow the diver to drift down current and to return to thestarting point on the return current.

Tidal changes often alter the direction of current andsometimes carry sediment-laden water and cause low visibil-ity within a matter of minutes. Tidal currents may preventdiving at some locations except during slack tides. Because aslack tide may be followed by strong currents, divers shouldknow the tides in the diving area and their effects.

Currents generally decrease in velocity with depth,and, therefore, it may be easier to swim close to the bottomwhen there are swift surface currents. Current directionmay change with depth, however. When there are bottomcurrents, it is recommended, whenever possible, to start theswim into the current rather than with the current; thisfacilitates the return to the entry point at the end of the divewith the current. Divers should stay close to the bottomand use rocks (if present) to pull themselves along.

Water temperature has a significant effect on the typeof equipment selected and, in some cases, determines thepractical duration of the dive. A thermocline is a boundarylayer between waters of different temperatures. Althoughthermoclines do not pose a direct hazard, their presencemay affect the selection of diving dress, dive duration, orequipment. Thermoclines occur at various depths, includ-ing levels close to the surface and in deep water.Temperature may vary from layer to layer. As much as a20°F (11C) variation has been recorded between the mixedlayer (epilimnion) above the thermocline and the deeperwaters (hypolimnion) beneath it.

Underwater visibility depends on time of day, locality,water conditions, season, bottom type, weather, and cur-rents. Frequently, divers will be required to dive in waterwhere visibility is minimal; sometimes, zero. Special precau-tions are needed. If scuba is used, a buddy line or other refer-ence system, and float are recommended. A convenient wayto attach a buddy line is to use a rubber loop that can beslipped on and off the wrist easily; this is preferable to tying aline that cannot be removed rapidly. The line should not slipoff so easily, however, that it can be lost inadvertently.

Heavy concentrations of plankton often accumulate atthe thermocline, especially during the summer and offshore

of the mid-Atlantic states. Divers may find that planktonabsorb most of the light at the thermocline and that eventhough the water below the thermocline is clear, a light isstill necessary to see adequately. Thermoclines in clearwater diffuse light within the area of greatest temperaturechange, causing a significant decrease in visibility.

WARNINGDIVERS SHOULD BE EXTREMELY CAUTIOUSAROUND UNDERWATER WRECKS OR OTHERSTRUCTURES IN LOW VISIBILITY TO AVOIDSWIMMING INADVERTENTLY INTO AN AREA WITHOVERHANGS.

A well-developed sense of touch is extremely impor-tant when working in low or zero underwater visibility.The ability to use touch cues when handling tools or instru-ments in a strange work environment is valuable to a diverin the dark. Rehearsing work functions on the surfacewhile blindfolded will increase proficiency at underwatertasks.

Underwater, low-light-level, closed-circuit televisionhas been used successfully when light levels are reduced,because a television camera “sees” more in these condi-tions than does the human eye. This is mainly true whenthe reduced visibility is caused by the absence of light; incases where the problem is caused by high turbidity, a TVcamera does not offer a significant advantage. When thepurpose of the dive is inspection or observation and aclosed-circuit television system is used, the diver servesessentially as a mobile underwater platform. The monitoris watched by surface support personnel who, in turn,direct diver movements. Underwater television cameras areavailable that are either hand held or mounted on thediver’s helmet.

Often a diver will be required to dive in water that con-tains either waterborne or sediment-contained contami-nants. The health hazards associated with polluted-waterdiving and the equipment to be used on such dives aredescribed in Chapter 13.

8.4 DIVING SIGNALS8.4.1 Hand Signals

Hand signals are used to convey basic information.There are various hand signalling systems presently in use.Divers in different parts of the country and the world usedifferent signals or variations of signals to transmit the samemessage. A set of signals used by NOAA is shown inFigure 8.2 and Table 8.4. The signals consist of hand,instead of finger, motions so divers wearing mittens canalso use them. To the extent possible, the signals werederived from those having similar meanings on land. Beforethe dive, the divemaster should review the signals shownwith all of the divers. This review is particularly importantwhen divers from different geographical areas constitute adive team, or when divers from several organizations are

Dive Planning 8-9

FIGURE 8.2Hand Signals

Stop Go Down/Going Down Go Up/Going Up Ok! Ok?

Something is Wrong

Out of Air LetÕs Buddy Breathe Danger

Distress(Need Help)

Ok! Ok?

Low on Air


FIGURE 8.2Hand Signals (continued)

Me, or watch me Come here Go that way I am cold

Which direction? Yes No Take it easy, slow down

Ears not clearing Hold hands Get with your buddy Look

You lead, IÕll follow What time? What Depth? I donÕt understand

Dive Planning 8-11

cooperating in a dive. Signal systems other than hand sig-nals have not been standardized. Whistle blasts, light flash-es, cylinder taps, and hand squeezes generally are used forattracting attention and should be reserved for that purpose.

8.4.2 Surface-to-Diver Recall SignalsUnexpected situations often arise that require divers to

be called from the water. When voice communication isnot available, the following methods should be considered:

• Hammer–rapping four times on a steel hull or metalplate

• Bell–held under water and struck four times• Hydrophone–underwater speaker or sound beacon• Strobe–used at night; flashed four times

8.4.3 Line SignalsWhen using surface-supplied equipment, use line sig-

nals either as a backup to voice communications to thesurface or as a primary form of communication. Whenusing scuba, divers may use line signals in conditions ofrestricted visibility, for diver-to-diver communications orto communicate with the surface. Table 8.3 describes linesignals commonly employed.

NOTEHand or line signals may vary by geographical areaor among organizations. Divers should review sig-nals before diving with new buddies or supportpersonnel.

8.4.4 Surface SignalsIf a diver needs to attract attention after surfacing and

is beyond voice range, the following signalingdevices/methods may be used:

• Whistle (diver or scuba air powered)• Flare• Flashing strobe• Flags• Hand/arm signals• Throw water into the air

8.5 AIR CONSUMPTION RATESWhen considering air consumption rates, three terms

need definition:

• Respiratory Minute Volume ( RMV ) is the total vol-ume of air moved in and out of the lungs in oneminute.

• Actual cubic feet (acf ) is the unit of measure thatexpresses actual gas volume in accordance with theGeneral Gas Law.

• Standard cubic feet (scf ) is the unit of measureexpressing surface equivalent volume, under stan-dard conditions,* for any given actual gas volume.

TABLE 8.3Line Pull Signals forSurface-to-Diver Communication

*Standard conditions for gases are defined as 32¡F(0C), 1 ata pressure, and dry gas.


In computing air consumption rate, the basic deter-minant is the respiratory minute volume, which is direct-ly related to exertion level and which, because ofindividual variation in physiological response, differsamong divers (Cardone 1982). See Table 8.5.Physiological research has yielded useful estimates ofrespiratory minute volumes for typical underwater situa-tions likely to be encountered by most divers (U.S. Navy1985). Table 8.6 shows these estimates. These estimatesof respiratory minute volumes apply to any depth andare expressed in terms of actual cubic feet, or liters, perminute (acfm or alpm, respectively).

The consumption rate at depth can be estimated bydetermining the appropriate respiratory minute volume forthe anticipated exertion level and the absolute pressure ofthe anticipated dive depth. This estimate, expressed in stan-dard cubic feet per minute (scfm), is given by the equation:

Cd = RMV (Pa)

whereCd = consumption rate at depth in scfm

RMV = respiratory minute volume in acfmPa = absolute pressure (ata) at dive depth

Problem:Compute the air consumption rate for a 50 ft. (15.2

m) dive requiring moderate work, maximum walkingspeed, hard bottom.

Solution:Cd = RMV (Pa)

RMV = 1.1 acfm (from Table 8.5)Pa 50/33 + 1 = 2.51 ata

Cd = (l.l acfm)(2.51 ata) = 2.76 scfm

Signal

Hand raised, fingers pointed up, palm toreceiver

Thumb extended downward from clenchedfist

Thumb extended upward from clenched fist

Thumb and forefinger making a circle withthree remaining fingers extended (if possi-ble)

Two arms extended overhead with finger-tips touching above head to make a largeÒOÓ shape

Hand flat, fingers together, palm down,thumb sticking out, then hand rocking backand forth on axis of forearm

Hand waving over head (may also thrashhand on water)

Fist pounding on chest

Hand slashing or chopping throat

Fingers pointing to mouth

Clenched fist, arms extended and forminga ÒXÓ in front of chest

Comment

Transmitted in the same way as a Traffic PolicemanÕsSTOP

Divers wearing mittens may not be able to extendthree remaining fingers distinctly (see various draw-ings of signal)

A diver with only one free arm may make this signalby extending that arm overhead with fingertips touch-ing top of head to make the ÒOÓ shape. Signal is forlong-range use

This is the opposite of OK! The signal does not indi-cate an emergency

Indicated immediate aid required

Indicates air supply is reduced to the quantity agreedupon in predive planning or air pressure is low andhas activated reserve valve

Indicates that signaler cannot breathe

The regulator may be either in or out of the mouth

TABLE 8.4Hand Signals

Meaning

STOP

GO DOWN orGOING DOWN

GO UP orGOING UP

OK! or OK?

OK! or OK?

SOMETHINGISWRONG

DISTRESS

LOW ON AIR

OUT OF AIR

LETÕS BUDDYBREATHE

DANGER

Dive Planning 8-13

TABLE 8.5Respiratory Minute Volume (RMV) at Different Work Rates

SLOW WALKING ON HARD BOTTOM UNDER WATERSWIMMING, 0.5 KNOT (SLOW)

SLOW WALKING ON MUD BOTTOM UNDER WATERSWIMMING, 0.85 knot (av. speed)MAX. WALKING SPEED, HARD BOTTOM U/W

SWIMMING 1.0 KNOTMAX. WALKING SPEED, MUD BOTTOM U/W

SWIMMING, 1.2 KNOTS

1216

202630

3535

53

0.420.60

0.710.921.1

1.21.2

1.9

Actual cubic ft / min (STP)Actual liters / min (STP)Activity Respiratory Minute Volume

LIGHTWORK

MODERATEWORK

HEAVYWORK

SEVEREWORK

19

20

22

23

24

26

27

28

29

31

32

33

35

36

37

39

40

41

42

44

45

46

48

49

50

52

1516171819202122232425262728293031323334353637383940

10 15 20 25 30 40 50 60 70 80 90 100 120 140 16021

23

24

26

27

29

30

31

33

34

36

37

39

40

42

43

45

46

47

49

50

52

53

55

56

58

24

25

27

28

30

32

33

35

36

38

40

41

43

44

46

48

49

51

52

54

56

57

59

60

62

64

27

28

30

32

34

36

37

39

41

43

45

46

48

50

52

54

55

57

59

61

63

64

66

68

70

72

28

30

32

34

36

38

39

41

43

45

47

49

51

53

55

57

58

60

62

64

66

68

70

72

74

76

33

35

37

39

41

44

46

48

50

52

55

57

59

61

63

66

68

70

72

74

77

79

81

83

85

88

37

40

42

45

47

50

52

55

57

60

62

65

67

70

72

75

77

80

82

85

87

90

92

95

97

100

42

44

47

50

53

56

58

61

64

67

70

72

75

78

81

84

86

89

92

95

98

100

103

106

109

112

46

49

52

55

58

62

65

68

71

74

77

80

83

86

89

93

96

99

102

105

108

111

114

117

120

124

51

54

57

61

64

68

71

74

78

81

85

88

91

95

98

102

105

108

112

115

119

122

125

129

132

136

55

59

62

66

70

74

77

81

85

88

92

96

99

103

107

111

114

118

122

125

129

133

136

140

144

148

60

64

68

72

76

80

84

88

92

96

100

104

108

112

116

120

124

128

132

136

140

144

148

152

156

160

69

73

78

82

87

92

96

101

105

110

115

119

124

128

133

138

142

147

151

156

161

165

170

174

179

184

78

83

88

93

98

104

109

114

119

124

130

135

140

145

150

156

161

166

171

176

182

187

192

197

202

208

87

92

98

104

110

116

121

127

133

139

145

150

156

162

168

174

179

185

191

197

203

208

214

220

226

232

TABLE 8.6Air Consumption Table at Depth

DEPTH (FEET)

SUR

FAC

E A

IR C

ON

SUM

PTIO

N R

ATE

(PSI

PER

MIN

UTE

)

Surf

ace


8.5.1 Determining Individual Air Utilization RatesAn alternative approach that can be used expresses

air utilization rates in terms of pressure drop in poundsper square inch (psi) rather than respiratory minute vol-ume. Keep in mind that usable cylinder pressure isdefined as the beginning cylinder pressure minus recom-mended air reserve (see Table 8.6). This technique allowsdivers to determine their Surface Air Consumption(SAC) rate which can be used to calculate estimated airconsumption rate at any depth. To determine the rate,read the submersible pressure gauges at the beginningand end of a dive to a constant depth. These readingsgive the information needed to use the simple four-stepprocedure shown below:

1. Subtract ending psi (as read from the submersiblepressure gauge) from the beginning psi to deter-mine the amount of air used during the timed dive(∆ psi).

2. Using the following formula, determine the diver’ssurface air consumption (SAC) rate:

∆psi/time (min) psi per minute on the surface (SAC)=

(depth in ft + 33)/33

3. Find the psi per minute on the surface on the leftside of the Air Consumption Table (Table 8.6) thatis closest to the estimated psi per minute. Readacross to the desired depth, which will give the esti-mated air consumption rate at depth.

4. To estimate how many minutes a cylinder of airwill last at that depth, divide the number of usablepsi in the cylinder (as shown on the submersiblepressure gauge minus a reserve amount) by the psiper minute used at that depth.

Problem:A diver swims a distance at 30 ft. (9.1 m) in ten min-

utes; the submersible pressure gauge reads 2,350 psi at thestart and 2,050 at the end of the timed dive, showing that atotal of 300 psi was consumed. What is the diver’s SAC?

The basic equation is:

∆psi/time (min)

(depth in ft + 33)/33

Solution:

300 (psi) ÷ 10 (mins) =

30 =

30 = 15.7 psi/min

(30 (depth) + 33)/33 (63/33) 1.9

The diver would consume 15.7 psi per minute at the sur-face. Knowing the consumption rate at the surface allows

the diver to use Table 8.6 to find the rate at any depth.The same information can be determined by multiplyingthe SAC figure times the depth of the planned dive inatmospheres absolute.

It is important to understand that individuals varysomewhat from day to day in their air consumption rates,and these calculations should thus be considered esti-mates only (Cardone 1982).

Problem:Convert SAC to cubic feet per minute (CFM) by mul-

tiplying the diver’s SAC times the cylinder constant (k)using formula:

RMV = SAC × k

Solution:The diver in this example had a SAC of 15.71 psi/min

using a scuba cylinder with a k factor of 0.0267 ft3/psi.

RMV= SAC × kRMV= 15.71 psi/min × 0.0267 ft3/psiRMV= 0.42 ft3/min

8.5.2 Scuba DurationKnowing the probable duration of the scuba air sup-

ply is vital to proper dive planning. With scuba, the dura-tion of the available air supply is directly dependent onthe consumption rate. Scuba air supply duration can beestimated using the equation:

Da =Va

Cdwhere

Da = duration in minutes Va = available volume in scf Cd = consumption at depth in scfm

The available volume depends on the type (rated vol-ume and rated pressure) and number of cylinders used,the gauge pressure measured, and the recommended min-imum cylinder pressure. Consumption rate depends onthe depth and the exertion level of the dive.

The “standard 80 cubic foot” aluminum cylinder hasan internal volume of 0.399 cubic feet (11.3 liters) at oneatmosphere. At its rated pressure of 3,000 psig, the cylin-der contains a deliverable volume of 81.85 cubic feet(2,317.7 liters).

For a given scuba cylinder, the ratio of rated vol-ume to rated pressure is a constant (k = Vr/Pr), mean-ing that a constant volume of air is delivered for eachunit of cylinder pressure drop. Mathematically, thisresults in a linear relationship between gauge pressureand deliverable volume. Figure 8.3 shows this relation-ship for a 71.2 ft3 (2,016 liters) steel cylinder and an 80ft3 (2,266 liters) aluminum cylinder. Deliverable vol-umes at any gauge pressure for these two cylinder types

SAC =

Dive Planning 8-15

can be read directly from Figure 8.3, or they can beindividually computed using the equation:

Vd = Pg x k

whereVd = deliverable volume in scfPg = gauge pressure in psig

k = cylinder constant

This equation can be used for any type of cylinder;see Table 8.7 for the appropriate cylinder constant.

For planning purposes, the available volume of air isthe difference between the deliverable volume at a givencylinder pressure and the recommended minimum cylin-der pressure. The recommended minimum cylinder pres-sures for the two most commonly used scuba cylindertypes are shown in Table 8.8. The available volume of airin the diver’s supply can be determined by the equation:

Va = N(Pg - Pm)k

whereVa = available volume in scfN = number of cylinders

Pg = gauge pressure in psigPm = recommended minimum pressure in psig


For planning purposes, estimates of cylinder durationare based on available air volumes rather than deliverableair volumes.

Problem:Estimate the duration of a set of twin 80 ft3 (2,318 liters)

aluminum cylinders charged to 2,400 psig for a 70 ft. (21.3m) dive for a diver with a RMV of 0.6 acfm.

Solution:The basic equation for duration is:

Da =Va

Cdwhere

Da = duration in minutesVa = available volume in scfCd = consumption rate at depth in scfm

Step 1:Determine Va using:

Va = N(Pg - Pm)kVa = 2(2,400 psig - 600 psig) (0.0266 scf/psig)

= 2(1,800 psig) (0.0266 scf/psig)= 95.76 scf

Step 2:Determine Cd using:

Cd = RMV (Pa)where

RMV = respiratory minute volume in acfmPa = absolute pressure at dive depth

Cd = 0.6 acfm 70 + l

33= 1.87 acfm

( )

FIGURE 8.3Deliverable Volumes at Various Gauge Pressures

TABLE 8.7Cylinder Constants


Step 3:Solve the basic equation for Da:

Da = VaCd

=95.76 scf

1.87 scfm

= 51.2 minutes

Table 8.9 shows estimates of the duration of a single alu-minum 80 ft3 (2,318 l ) cylinder at five exertion levels for vari-ous depths. These estimated durations are computed onthe basis of an available air volume of 64.1 ft3 (Va = 3,000psig - 600 psig) (0.0267 ft3/psig).

8.5.3 Scuba Air RequirementsTotal air requirements should be estimated when

planning scuba operations. Factors that influence thetotal air requirement are depth of the dive, anticipatedbottom time, normal ascent time at 30 ft/min (9.1m/min), any required stage decompression time, andconsumption rate at depth. For dives in which directascent to the surface at 30 ft/min (9.1 m/min) is allow-able, the total air requirement can be estimated using theequation:

TAR = tdt (Cd)

where TAR = total air requirement in scf

tdt = total dive time in minutes(bottom time plus ascent time at 30 ft/min)

Cd = consumption rate at depth in scfm

Problem 1:Estimate the total air requirements for a 30-minute

dive to 60 ft. (18.3 m) for a diver with a RMV of .92acfm.

Solution:Step 1:

Determine tdt. Total dive time is defined as the sumof the bottom time and normal ascent time at 30 ft/min(9.1 m/min):

tdt = 30 + 2 = 32 mins

Step 2:Determine Cd using the equation:

Cd = RMV (Pa)RMV = 0.92 acfm

60Pa = + 1 = 2.81 ata33

Cd = (0.92 acfm) (2.81 ata)= 2.59 scfm

TABLE 8.8Scuba Cylinder Pressure Data

TABLE 8.9Estimated Duration of 80 Ft3 Aluminum Cylinder

500500

22503000

24753000

Steel 72Aluminum 80

430600

29.114.69.77.35.84.8

42.721.414.210.78.57.1

58.329.219.414.611.79.7

91.645.830.522.918.315.3

256.4128.285.564.151.342.7

1.02.03.04.05.06.0

0336699

132165

ata ** *

*

**

Step 3:Determine TAR using the equation:

TAR = tdt (Cd)= (32 mins) (2.59 acfm)= 82.88 scf

For dives in which stage decompression will be neces-sary, the total air requirement can be estimated using theequation:

TAR = Cd (BT + AT) + Cd1T1 + Cd2T2 + Cd3T3 (etc.)

where Cd1T1, Cd2T2, are the air consumption rates andtimes at the respective decompression stops.

Problem 2:Estimate the total air requirement for an 80-minute diveto 60 ft. (18.3 m) for a diver with a RMV of 0.6 acfm.

Solution:Step 1:Determine Cd and Cd1 using the equation:

Cd = RMV (Pa)= (0.6 acfm) (2.8 ata) = 1.68 scfm

Step 2:Determine the total time for the dive, ascent, and

decompression stops. For the dive and ascent to the sur-face, add the bottom time (BT) and the ascent time(AT) (to the nearest whole minute) at 30 ft/min (9.1m/min).

BT + AT = 80 + 2 = 82 mins

This dive requires a 10-ft. decompression stop. At anascent rate of 30 ft/min, it will take two minutes toascend from 60 ft. (18.3 m) to the surface.

The time required for decompression at 10 ft. (3 m)is 7 minutes, according to the USN Standard AirDecompression Table for a dive to 60 ft. for 80 min-utes.

Cd1 = 0.6 10

+ 1 = 0.78 scfm33

(Assume same RMV on decompression stop.)

Step 3:Determine TAR using the equation for this case:

TAR = Cd (BT + AT) + Cd1T1= (1.68 scfm) (62 mins) + (0.78 scfm) (7 mins)= 104.2 + 5.5 = 109.7 scf

Computation of these estimates during predive plan-ning is useful to decide whether changes in assigned tasks,task planning, etc. are necessary to ensure that the divecan be conducted with the available air supply. However,positioning an auxiliary cylinder at the decompressionstop is considered a safer practice than relying on calcula-tions of the available air supply.

8.5.4 Surface-Supplied Air RequirementsEstimations of air supply requirements and duration of

air supplies for surface-supplied divers are the same as thoseof scuba divers except when free-flow or free-flow/demandbreathing systems are used; in these cases, the flow, in actu-al cubic feet per minute is used (in all calculations) insteadof RMV (see Table 8.10). Also, the minimum bank pressuremust be calculated to be equal to 220 psig plus the absolutepressure of the dive (expressed in psia).

Problem:Estimate the air requirements for a 90 ft. (27.4 m)

dive for 70 minutes with a demand/free-flow helmet. Thisdive requires decompression stops of seven minutes at 20ft. (6.1 m) and 30 minutes at 10 ft. (3 m).

Solution:

TAR = Cd (BT + AT) + Cd1T1 + Cd2T2where

TAR = Total Air RequirementCd = Consumption rate at depth (scfm)BT = Bottom time (mins)AT = Ascent timePa = Pressure in ata

Step 1:Determine Cd, Cd1, Cd2:

Cd = flow x Pa= (1.5 acfm)(3.73 ata) = 5.6 scfm

Cd1 = (1.5 acfm)(1.61 ata) = 2.4 scfmCd2 = (1.5 acfm)(l.30 ata) = 2.0 scfm

Step 2:TAR = Cd (BT + AT) + Cd1 T1

= 5.6 scf (70 + 3 mins) + 2.4 scf (7 mins) + 2.0 scf (30 mins)

= 409 scf + 17 scf + 60 scf= 486 scf

Cylinder constants for large high-pressure air/gas stor-age systems are determined in the same fashion as thosefor scuba cylinders, i.e., rated volume/rated pressure = k.

The procedure for determining available volume ofair is also the same as for scuba. For example,

Va = N(Pg - Pm) k

Dive Planning 8-17

( )

whereVa = available volume (scf)N = number of cylinders

Pg = gauge pressure (psig)Pm = minimum reserve pressure (psig)


NOTEIf cylinder banks are used as a back-up to a com-pressor supply, the bank must be manifolded withthe primary source so that an immediate switchfrom primary to secondary air is possible (seeFigure 6.10).

Problem:Determine the number of high-pressure air cylinders

required to supply the air for the above dive (486 scf ) ifthe rated volume equals 240 scf, rated pressure equals2,400 psi, and beginning pressure equals 2,000 psi, using aminimum reserve pressure of 220 psi.

Solution:

Step 1:How much air could be delivered from each cylinder?

Va = N(Pg - Pm)k

240 scfk = = 0.1 scf/psi

2,400 psi

Pm = 220 psi + 90 + 33 × 14.7 = 275 psi33

Va = 1(2,000 - 275) × 0.1Va = 172.5 scf/cylinder

Step 2:How many cylinders would be required in the bank to sup-ply the required amount of gas?

vol. required 486 scfN = = = 2.8 or 3 cylinders

vol/cyl 172.5 scf/cyl

NOTECalculations for gas supply requirements or scubaduration are for planning purposes only. The diverand tender must continuously monitor the gassupply throughout the dive.


TABLE 8.10Flow-Rate Requirements for Surface-Supplied Equipment

Equipment Type

Demand/freeflowFree flow

Flow Rate

1.5 acfm6.0 acfm

NOTE: Significant variations in these values canoccur, depending on the flow-valve set by the diver.Therefore, these values are minimum estimates.

( )

The NOAA Diving Manual was prepared jointly by the National Oceanic andAtmospheric Administration (NOAA), U.S. Department of Commerce and BestPublishing Company.

This CD-ROM product is produced and distributed by the National Technical InformationService (NTIS), U.S. Department of Commerce.Visit our Web site at www.ntis.gov.

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