Pro­pel­ler strikes are one of the most se­ri­ous but pre­ventable mishaps out at sea. Learn more about the safety pro­to­cols that can help you stay safe while sur­fac­ing

Asian Diver (English) - - Courses - By Brit­tany Trout

As scuba divers, it is in­evitable that we share the wa­ter with boats and of­ten rely on boats to get us to and from dive sites. There­fore, it is vi­tal that boat op­er­a­tors and divers are equipped with skills and in­for­ma­tion to help pre­vent pro­pel­ler strikes.

At DAN AP, we are run­ning a tar­geted safety cam­paign fo­cused on pro­pel­ler in­juries and boat aware­ness as we con­tinue to see se­vere in­juries and loss of life re­sult­ing from avoid­able pro­pel­ler strikes. In fact, there have been 31 known scuba/snorkelling fa­tal­i­ties at­trib­uted to boat/pro­pel­ler strikes in the Asia-Pa­cific re­gion be­tween 2009 and 2018. This fig­ure is likely to be much higher, as many in­ci­dents go un­re­ported.

Although laws vary by coun­try (and state), divers should gen­er­ally stay within 100 me­tres of a diver-be­low flag in open wa­ter. When sur­fac­ing, you should stay as close to the flag as pos­si­ble. Un­for­tu­nately, many boat op­er­a­tors are not fa­mil­iar with the flag’s mean­ing, or the re­lated laws and will still come within ex­clu­sion zones. The safest place for any diver on or near the sur­face is as close to the dive flag as pos­si­ble.

Our sta­tis­tics high­light that there is a larger in­ci­dence of pro­pel­ler-re­lated ac­ci­dents oc­cur­ring within de­vel­op­ing coun­tries in the Asia-Pa­cific.

Why is this?

• The train­ing and reg­u­lat­ing of boat driv­ers is not as strin­gent in de­vel­op­ing coun­tries as it may be in other parts of the world

• There is a gen­eral lack of aware­ness of dive flags

In ad­di­tion, in the event of an in­ci­dent, med­i­cal fa­cil­i­ties in re­mote parts of these coun­tries are ba­sic and not as well-equipped to deal with se­vere trauma.

If you are div­ing or snorkelling in de­vel­op­ing coun­tries of the Asia-Pa­cific, or any­where else in the world, use sig­nalling tools, lis­ten care­fully and be aware of boat move­ment while at or com­ing to the sur­face.


Dive flags. Fly­ing a dive flag can be an ef­fec­tive, and in some places re­quired, means of alert­ing boats that divers are in the wa­ter. The two types of flags most com­monly recog­nised in re­la­tion to div­ing are the al­pha flag and the diver down flag.

The in­ter­na­tion­ally recog­nised al­pha flag is flown when the mo­bil­ity of any ves­sel is re­stricted, in­di­cat­ing that other ves­sels should yield the right of way.

This flag can be flown along with the diver down flag when divers are in the wa­ter, be­cause dive boats must main­tain a close vicin­ity to the divers and can­not quickly move. The al­pha flag in­di­cates that divers are in the area. How­ever, it also has other uses.

A diver down flag is rec­om­mended to alert ves­sels dur­ing shore div­ing. A float­ing buoy teth­ered to a dive reel can be used to sig­nal where divers are lo­cated in the wa­ter. A reel tow­ing a float­ing dive flag should never be at­tached di­rectly to the diver. Car­ry­ing the reel helps pre­vent the diver from be­ing dragged in case the flag is caught by a pass­ing boat.

Whether the dive flag is flown on a boat or a buoy marker, the flag should be in good con­di­tion to en­sure vis­i­bil­ity. Re­place the flag when the safety in­tegrity is com­pro­mised by faded colour or rips. The diver down flag should be at least 50 cen­time­tres by 60 cen­time­tres (or as dic­tated by lo­cal laws) and flown above the ves­sel’s high­est point. When dis­played from a buoy, the flag should be at least 30 cen­time­tres by 30 cen­time­tres. Al­ways make sure the flag is vis­i­ble from all direc­tions.

Sur­face mark­ers. Safety tools such as sur­face marker buoys (SMBs), whis­tles and other audi­ble sig­nals, dive lights and sig­nalling mir­rors can be used to com­mu­ni­cate your lo­ca­tion to boaters af­ter you as­cend from a dive. An SMB may be used in ad­di­tion to a dive flag for alert­ing boaters that divers are in the wa­ter. Be­fore the dive, re­view how to de­ploy the SMB to be pre­pared for us­ing it on as­cent.

When us­ing sig­nalling de­vices, divers should never as­sume they are vis­i­ble to boat op­er­a­tors

When us­ing sig­nalling de­vices at the sur­face, divers should never as­sume they are vis­i­ble to boat op­er­a­tors. Glare from the sun, waves, pas­sen­gers, weather con­di­tions and other fac­tors can make notic­ing a diver in the wa­ter dif­fi­cult.

Be At­ten­tive Un­der­wa­ter

In ad­di­tion to us­ing sig­nalling de­vices and pay­ing at­ten­tion to boat traf­fic top­side, divers must be aware of pass­ing boats when they are un­der­wa­ter. Look­ing and lis­ten­ing for boats over­head is a good prac­tice but keep in mind that poor vis­i­bil­ity and sound lo­cal­i­sa­tion when un­der­wa­ter can in­ter­fere. In most cases, a diver should be able to hear a boat from un­der­wa­ter, but it may be dif­fi­cult to lo­calise the di­rec­tion from which the sound is com­ing be­cause sound trav­els ap­prox­i­mately four times faster in wa­ter than in air. Wear­ing a hood may al­ter hear­ing thresh­olds even more.

A safety stop at five me­tres al­lows a diver to de­crease ni­tro­gen up­take and is also an op­por­tu­nity to scan for boat traf­fic be­fore as­cend­ing to the sur­face. Divers should be care­ful not to rely on quick re­ac­tion time in the event that they must move away from a pass­ing boat while un­der­wa­ter. A boat can rapidly close in on an un­know­ing diver with­out al­ways grant­ing enough time to move a safe dis­tance away. For these rea­sons, it is not ad­vis­able for divers to rely on ob­serv­ing for boats un­der the sur­face with­out a sur­face sig­nalling de­vice.

Have an Ac­tion Plan

A plan for treat­ment and evac­u­a­tion of a diver struck by a boat or pro­pel­ler should be in place be­fore ar­rival at the dive site. To treat a lac­er­a­tion wound, stem the loss of blood by ap­ply­ing di­rect pres­sure to the wound im­me­di­ately, and then ap­ply­ing pres­sure bandages. If there is an am­pu­ta­tion of the arm or leg, a tourni­quet (ap­plied by some­one with ap­pro­pri­ate train­ing) may be the best, or only, way to stem the bleed­ing. A vic­tim of se­vere bleed­ing needs ur­gent med­i­cal at­ten­tion. Move­ment should be min­imised and oxy­gen first aid pro­vided as it can re­duce the ac­com­pa­ny­ing shock. Know who to call and what role oth­ers play in re­spond­ing to a med­i­cal emer­gency.

Re­search and Preven­tion

DAN Asia-Pa­cific is cur­rently run­ning a Pro­pel­ler In­juries & Boat Aware­ness Safety Cam­paign to cre­ate aware­ness amongst boat op­er­a­tors and divers on how to safely share dive sites.

To re­port a div­ing-re­lated in­ci­dent, we en­cour­age you to share the in­for­ma­tion via a form avail­able on the Ac­ci­dent Re­port­ing & Re­search sec­tion of the DAN AP web­site. The in­for­ma­tion on re­ported cases is used for case sum­maries and to cre­ate preven­tion ma­te­ri­als.

TOP The diver down flag should be flown above the ves­sel’s high­est point

ABOVE Sur­face marker buoys (SMBs) can be used to com­mu­ni­cate your lo­ca­tion to boaters af­ter you as­cend

ABOVE Pro­pel­lor in­ci­dents are pre­ventable as long as both divers and boat op­er­a­tors are alert and aware

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