Diving  is a  potentially  hazardous  activity.  The materials  contained within  this  magazine  are for informational purposes only and are not intended as a substitute for proper and appropriate training.

Diving Talk: Underwater Communications

Although  never, 'The Silent World', the  physical  limitations  of  a water environment continues to  pose problems  for divers intent on communicating  effectively with their companions, or with the surface.  While  advances  in  surface-to-diver, diver-to-diver  voice  communications  systems have had an enormous impact on  occupational diving safety, the use of such devices by the  recreational SCUBA diving community  has met with limited  success; not least because few  recreational  divers require  such complex -  or  costly -  communication systems; especially when there  already exists a variety of  time-honoured techniques that usually prove adequate to their needs.

Although able to  be adapted to suit a variety of  environmental conditions, the worth of each  method is  only as good  as the diver's understanding  of the 'language' being used  and - through  practice - their  proficiency in its  use.  In that regard  the more 'languages' that a diver understands, the better equipped they will be to communicate their intentions effectively with others when the need arises. Diving  communications - whether  between divers  underwater, or between  divers on the surface and the control position - fall under  three broad headings: visual, manual, and sound.

Visual Hand Signals Universally  taught as the primary  means of  underwater  communication  when diving recreationally,  a hand  signal's effectiveness  relies on divers  being in  visual contact with  one  another:  In  that  regard their  value is  limited  by visibility, the  ability to attract  another  diver's  attention,  and   how  well  the  signals   are  executed  and interpreted. In  the same way that some people have difficulty  in communicating the spoken word because  of a tendency to  mumble, hand  signals should be  theatrical flourishes that leave no doubt as to their meaning. In a  well-planned dive,  there  is  often  little need  to  communicate  anything  more elaborate  than basic intentions or  to draw  attention to  difficulties.  However,  it  is worth  remembering that  regional variations  in hand  signals  do  exist.  One person's "ascend"  sign may  be  interpreted  by another  diver  as  the, "OK"  signal!  For  that reason  alone, a review of hand signals and  their meanings should be a key part of all pre-dive briefings.

Reproduced from PADI Open Water Manual, courtesy of PADI

Numeric Hand signals

One

Two

Three

Four

Five

Six

Seven

Eight

Nine

Ten

Reproduced from, ' Doing It Right: The Fundamentals of Better Diving', courtesy of Jarrod Jablonski

Although  it's a  small 'vocabulary' that  is quickly and easily  learned,  surprisingly  few divers  know - or use  and understand - anything  other than a  very few  of the basic hand signals.

Written Communications Useful for  recording details of a dive, (sketching features of a wreck, for example) and for  noting  in   advance  key  aspects  of  a   complicated  dive  plan  -   like  planned decompression stops  that can  then be  carried with the diver and referred to at will - slates and  wet-notes also  allow divers to  communicate with  one another  using  the written word. Wasteful in terms of the time taken to jot  down a message and then for another diver to read and comprehend  its meaning, written  communication lacks  the immediacy  of other techniques.  It is also dependent on  the divers being close together, reasonably good visibility, and how legible the handwriting, (particularly when the writer is wearing thick gloves; has cold hands and numb fingers; or is affected by narcosis!)

Light Signals Apart from providing essential  illumination in conditions with low ambient light, (as in a night dive or penetration dive) an  underwater  light is also a communication device for use above and below the surface. On the  surface, at  night, it can  be used to  indicate  to boat or  shore whether  the diver is OK, or in need of help?  Underwater,  it can  be used as an attention-getter by moving the light  beam rapidly back and  forth in  front of a buddy and then directing it onto, for example, a hand-signal  or contents  gauge.  (Under no circumstances should the light ever be shone directly into another diver's eyes!)  Dependent on  good visibility to be  effective, lights are  ill suited to underwater use in turbid   waters,   where  the   reflected   backscatter   from   particles   can   lead  to disorientation.

You can use hand signals at night by shining your light on your hands

Reproduced from PADI Adventures in Diving Manual, courtesy of PADI

Flags Flown from  a vessel tendering  to divers, or  from a  tethered  surface  safety  float - especially when  diving in waters with  busy surface traffic  - the  diving flag indicates that  divers  are below.  Ideally the  flag should  be rigid  and  clearly  recognisable for what it  signifies.  While there  are regional variations  in the flag  used - most often in inland  waterways - Flag  Alpha has  international recognition.  Nevertheless, the rules governing  its use and  the precautions  that other surface craft are expected to take when approaching a vessel or float displaying the flag will vary.

Manual Line Signals The widespread introduction of  voice communication systems has, in many instances, made the use of line signals almost redundant.  Often considered an anachronism that has  little place in today's  high-tech world  of diving - particularly  by  free-swimming divers engaged in scuba operations - a good  knowledge of life-line signals  should still be a part of every working diver's basic repertoire of skills. For tethered  divers line signals provide a back-up  communications method should the primary   system   fail.   Divers  on   scuba,   particularly   in   reduced  visibility,  can communicate  their  intentions  via the  buddy-line  or  by  tactile  pressure,  ie. hand squeezing.  If  using a  surface marker  buoy or  safety float  a surface  observer  can visually  monitor the diver  by the  bobbing  of the  marker  or, from  a boat,  transmit messages through the safety line to the diver below.

Whenever life- or safety  lines are used there  are a number of  considerations to bear in mind.  The  line should  be  secured  to the diver's  safety harness  using a  bowline knot.  The inboard  end of the line  must be similarly  secured, either to the  vessel or surface  marker buoy, and  the line kept free of slack.  (A good tender  should be able to 'feel' the diver at all times without putting an undue strain on the line.) Signals  made  with a line  are of two  types:  The  PULL - a  long,  steady  and  very distinct tug  on the line, and the  BELL - a short, sharp  pull with  the same timing and sequence  as that of striking  a ship's bell (i.e. 5 bells  =  Ding-Ding:  Ding-Ding; Ding)

Any  communication  via  the  line,  either  surface-diver,  or  diver-surface,  must  be acknowledged  by returning  the  same  signal.  (Except  for the  emergency  signal, a succession of pulls, which must be acted upon immediately.) All of the  signals are preceded  by one pull  on the  line  to attract  attention and are then  made once either  the diver or the  attendant  has acknowledged  with a return pull.  When a signal  is received it  is repeated back  to the sender  to indicate that it has  been properly  interpreted.  (Although  it  should be  remembered that  a working diver may not always be  in a position to respond immediately, requiring  the tender to wait a short while before again repeating the signal.) The beauty  of line signals is that  not only are  they easy to  learn - and remember - but they can be readily adapted to  underwater sound communication, either between the surface  and the  diver  or diver  to diver,  by simply  tapping  'Pulls  and  Bells' on suitable metal objects beneath the surface.

Buddy Lines Although  there's  seldom  a need for their use in 'normal' recreational  diving,   buddy lines  that   link  a    pair  of divers   together   offer  the same  facility   for   passing messages   back  and  forth between  them  as   does  a surface-to-diver umbilical. Tactile Signals There  would  be few divers who,  at  one  time  or  an- other, have not experienced some    minor     degree   of anxiety  about  the dive.  In those    situations   contact with  another  human  being will usually  have  a positive and re-assuring effect. In certain  situations, (such as a silt-out; a catastrophic failure of a primary and back -up  light;  or  an equipment failure)   it   may   often  be necessary    for   divers   to swim  together side-by side. Holding  hands  may  not do much  for  a  macho  diver's image,   but   it   does  help maintain  contact; can have a calming  influence  on  the diver  being   assisted,  and does   allow   for   commun- ication       through     hand pressure. Once   again  the  Pulls  and Bells   code   used    in  line signals    can    be    readily adapted to  hand squeezes.   Sound Noise Makers A  denser  medium  than air, water is  a good  conductor of sound.  This property has both      advantages     and disadvantages  to the diver. On  the plus  side,  sound is magnified and  can be heard over  vast  distances.   The downside  is   that  because sound  travels  more quickly through  water,  the source and    direction     may    be difficult to determine.

Single-Lifeline Code Attendant to Diver General Signals 1 Pull   -  To call attention prior to sending a message,               or to check that diver is OK? 2 Pulls  -  Am sending down a rope's end (or as               previously arranged.) 3 Pulls  -  You have come up too far.               Go down slowly till we stop you. 4 Pulls  -  Come Up. 4 Pulls followed by 2 Bells           -  Come up, hurry up. 4 Pulls followed by 5 Bells           -  Come up to your safety float. Direction Signals 1 Pull   -  Search where you are. 2 Bells  -  Go to the end of distance line or Jackstay. 3 Bells  -  Face shot line then go right. 4 Bells  -  Face shot line then go left. 5 Bells  -  Come into the shot line or turn back if on              a jackstay. Diver to Attendant General Signals 1 Pull   -  To call attention.               Made bottom.               Left bottom.               Reached end of jackstay.               I am well. 2 Pulls  -  Send me down a rope's end (or as               previously arranged) 3 Pulls  -  I am going down. 4 Pulls  -  May I come up? 4 Pulls followed by 2 Bells           -  I want to come up.              Assist me up. 4 Pulls followed by 5 Bells           -  May I come up onto my safety float? Succession of Pulls (must be more than 4)           -  EMERGENCY SIGNAL.              Pull me up IMMEDIATELY Succession of 2 Bells           -  Am foul and need the assistance of another              diver Succession of 3 Bells           -  Am foul but can clear myself if left alone. 4 Pulls followed by 4 Bells           -  Attend telephone. Working Signals 1 Pull   -  Hold on or stop 2 Bells  -  Pull up. 3 Bells  -  Lower 4 Bells  -  Take up slack lifeline, or               You are holding me too tight. 5 Bells  -  Have found, started, or completed work.

A  system  that  lends  itself  to  basic  communications,  regardless  of  visibility  and distance between  the  divers, sound  signals  are  the  simplest  form  of  underwater communications.  Many dive knives  still feature a metal boss that can be used to tap against the  sides of a cylinder; elastic  tubing threaded with  hardwood beads can be placed around the cylinder  and used as a tank-banger; or - and growing in popularity - attention-getting  devices such as the Mini-Hammerhead,  an  air activated  gadget that attaches  between the  L.P. hose  and  the B.C. inflator hose.  All  of  these  are effective in  diver-to-diver communications, either  as a stand-alone system based on a pre-arranged  code, or to  attract the  attention of  a buddy  as a prelude to using, say, hand-signals. Applying  the K.I.S.S. (Keep  It  Simple,  Stupid)  principle  to  as  much  of  diving  as possible, sound  codes are  something that  should be agreed upon in advance  of the dive and reduced to an elementary  minimum.  Just as with  Sign language, knowledge of the Morse code has little practical  relevance for most divers.  In that regard, basic line signals translate well into sound communications.

Sound  can   also  be  used  effectively   in  surface-to-diver   communication  and  is especially  useful in  recalling  them back  to  the surface.  Because  of environmental considerations  - as well as  restrictions on their  availability  -  explosive  devices like 'thunderflashes' that can be weighted to detonate at depth are now seldom used. Metal  diving ladders - or,  at a  pinch, the  metal  hulls  of  vessels - can  be used as sound conductors by hitting them with a large  hammer, wrench, or spare dive weight. More expensive  to justify and  maintain, underwater  speakers  and purpose-designed horns perform a similar function. Attracting the attention  of the shore, a boat, or  other divers when on the surface is made easier when a diver carries a whistle for just such purposes.  While they're more easily heard than a shout, whistles have the  added advantage of being more efficient in terms of  the energy that a diver  expends in  attracting attention.  Their  use  also reduces the risk of distress through inadvertently swallowing water while the mouth is wide open!

Voice Communications Primarily used by working divers  spending extended periods of time at depth, or those -  like   military,  police   and   rescue   divers  -  with   other  special   needs,   voice communication  systems fall  into two  broad  categories,  hard-wire, (those  in which sender and receiver are linked by a carrier cable) and wireless. While each lends itself to particular diving  applications, both suffer from the fact that water is an unsympathetic medium when it comes to  electronics and the transmission of intelligible sound! The prime requirement in voice communication systems is the need for an air pocket in front of  the diver's mouth.  This  is seldom  an issue in surface  supplied diving where helmets and full-face  masks are used, and  where the  hard-wire cable forms  part of the  umbilical  system.  But even then  communications may be  hampered by ambient noise  from  the inlet valve,  by  exhaust  bubbles, or even  by the  density of the gas being  breathed.  (In  helium  rich  atmospheres,  for  example,  voice  distortions  are corrected through the use of a compensating "de-scrambler".)

Although better  suited to the needs of  un-tethered  SCUBA divers, wireless  systems pose their own problems in terms of through water communications.  Most incorporate an  oral-nasal  pocket  and  require  the  diver  to carry a  transducer, a power  pack, microphone  and a  receiver,  relatively  bulky  items  that all  have  their  own  failure points.  Although  the introduction  of digital technology  has improved  the quality  of reception, many  have limited  range and  effectiveness.  (Thermoclines,  for example, may act as a barrier to receiving or transmitting a message.)    Usually  expensive  and  high  maintenance  items  that  -  in  their  present  state  of development - seem to offer few cost/benefit advantages for most recreational diving situations,  voice   systems  depend  on  distinct,  unhurried  and  clearly  enunciated speech.  Neither  are they really  suited  to providing a running commentary on a dive, particularly in a SCUBA application  where talking will quickly  deplete the available gas supply.  Ideally  voice messages should  be brief and relevant - and  repeated back by the  receiver to indicate  that they  have been  properly  understood.  In  that regard voice communications  only complement  the need  that divers  have to know a broad range of underwater 'languages'.

Talking Underwater Hardly a method  that's to be recommended - and one  that best lends itself to divers with short  hair and not wearing  a hood - SCUBA  divers  with conventional  regulator mouthpieces can 'speak' to each other  by placing their heads  together - side by side while  facing  one  another  -  and  then,  while  talking  into  the  mouthpiece  of the regulator, allowing the sound to be conducted  through the skull bone  above the ear. While  this technique can  be very effective,  it's one that should  be used judiciously. Its use  may communicate the wrong  impression to  other divers who  witness two of their companions apparently locked together in an underwater embrace!