Diver communications

Diver communications

Diver communications are the methods used by divers to communicate with each other or with surface members of the dive team.

There are several distinct forms of diver communications:

  • Voice communications - Most professional diving equipment such as full face diving masks and diving helmets include voice communication equipment
  • Video communications - Surface supplied divers often carry a closed circuit video camera on the helmet which allows the surface team to see what the diver is doing and to be involved in inspection tasks. This can be used to transfer signals to the surface if voice comms fails, and is in itself a one way mode of communicating useful data to the surface.
  • Text communications - Underwater slates may be used to write text messages which can be shown to other divers, and there are some dive computers which allow a limited number of pre-programmed text messages to be sent through water to other divers or surface personnel with compatible equipment.[citation needed]
  • Non-verbal communications:
  • Hand signals - Recreational divers do not usually have access to voice communication equipment, and it does not generally work with a standard scuba demand valve, so they use other signals. Hand signals are generally used when visibility allows, and there are a range of commonly used signals, with some variations. These signals are often also used as an alternative by professional divers
  • Line signals (rope pulls) - Rope signals can be used if the diver is connected to another diver or tender by a rope or umbilical. There are a few partly standardised codes using "pulls" and "bells" (a pair of short tugs). These are mostly used as backup signals by professional divers in the event that voice communications fails, but can be useful to recreational and particularly technical divers, who can use them on their surface marker buoy lines to signal to the surface support crew.
  • Light signals - Made using an underwater torch at night. There are not many standard light signals. Suitably skilled divers can transmit morse code using a light.
  • Cave line symbols - these are symbols attached to cave lines, indicating critical information such as the direction to the exit.
  • Sign language Divers who are familiar with a sign language such as American sign language and equivalents may find it useful underwater, but there are limitations due to the difficulty of performing some of the gestures intellibly underwater with gloved hands and often while trying to hold something.
  • Tap codes - made by knocking on the walls, are used occasionally to communicate with divers trapped in a sealed bell or the occupants of a submersible during a rescue.
  • Rattle - a tube containing ball bearings used by guides of large groups to attract attention.
  • Miscellaneous emergency signals - Including the use of mirrors, compressed air sirens, whistles, noisemakers, colour coded Delayed Surface Marker Buoys etc, to alert the surface support personnel of a problem
  • Diver down signals - The dive flags, lights and shape signals used to indicate the presence of divers in the water.


Voice communications

Both hard-wired (cable) and through-water electronic voice communications systems may be used with surface supplied diving. Wired systems are more popular as there is a physical connection to the diver for gas supply in any case, and adding a cable does not make the system any different to handle. Wired communications systems are still more reliable and simpler to maintain than through-water systems. The communications equipment is relatively straightforward and may be of the two-wire or four-wire type. Two wire systems use the same wires for surface to diver and diver to surface messages, whereas four wire systems allow the diver's messages and the surface operator's messages to use separate wire pairs.

A standard arrangement with wired diver communications is to have the diver's side normally on, so that the surface team can hear anything from the diver at all times except when the surface is sending a message. This is considered an important safety feature, as the surface team can monitor the diver's breathing sounds, which can give early warning of problems developing, and confirms that the diver is alive.

Divers breathing helium may need a decoder system which reduces the frequency of the sound to make it more intelligible.

Through water communications systems are more suitable for scuba as the diver is not encumbered by a communications cable, but they can be fitted to surface supplied equipment if desired. Most through water systems have a Push To Talk (PTT) system, so that high power is only used to transmit the signal when the diver has something to say. For commercial diving applications this is a disadvantage, in that the supervisor can not monitor the condition of the divers by hearing them breathe.

Dry bells may have a through water communication system fitted as a backup.[1]

Hand signals

Hand signals are a form of sign system used by scuba divers to communicate when underwater.

In most situations simple hand signals are used. The most basic ones are:

  • Signal for "Let's go up"
    Thumb up = "let's go up"
  • Thumb down = "let's go down"
  • Circle with thumb and index finger, while other fingers may be straight or curved with the index finger = "I'm OK" or "Are you OK?" (Because divers sometimes wear mittens, this gesture can also be made without fingers extended - this variant can be used even by divers who are not wearing mittens at the time.)
  • "Cutting" or "chopping" throat with a flat hand = "I'm out of air".[2][3]
  • pointing to the mouth with thumb and fingers together, moving hand back and forth a short distance = "Give me air now" (emergency implied)
  • Wobbling a flat hand = "I have a minor problem"
  • Waving one or both arms in a wide arc = "Emergency! Help me now" on the surface.
  • Hugging chest = "I am cold!"
  • Hands indicating rising and falling chest = "I am out of breath!"[2][3]
  • A diver giving the signal for cramping
    Repeatedly clenching and unclenching fist = "I have a cramp"
  • Shrugging shoulders, arms bent, palms up = "I don't know"
  • One hand held flat while placing index and middle finger of the other hand on the palm = "How much air do you have left?".

Hand signal variations

Diving signals sometimes differ between groups of divers. Some variations include:

  • The throat cut signal: "general danger" or "emergency".
  • Pointing with a clenced fist: "Danger in that direction"
  • Tapping the mouthpiece: "I'm out of air".
  • Pointing at the ear: "I can't clear that ear"; or "listen!"
  • Pointing at someone: changes the reference of the next signal from "I" to the diver pointed at.
  • Pointing at side of head with screwing movement: "I am dizzy"; or "there is a boat moving about" (the screwing represents a propeller).
  • First finger up/down: "let's go up/down".
  • Thumb up: "I am OK" (often with naval divers)[citation needed]
  • Forming a large circle with both hands above the head: "I'm OK", Used at the surface as the OK sign can be difficult to see from a distance.
  • Touching or tapping the top of the head with elbow extended sideways: "I'm OK" at a distance. Common in Monterey, California and Ontario, Canada.
  • Index fingers of both hands extended, brought together repeatedly = "let's buddy up"
  • Fist half-clenched with palm side held facing the regulator while moving away/closer to the mouth = "Share air"
  • Thumb up and forefinger pointed in specific direction = "Terminate dive, that is the way out" used to signal time to surface when under an overhead, as inside a cave or wreck.
  • Flat hand swept over top of head, palm down = "I have a ceiling". This can indicate the diver has gone into decompression obligation or that there is a solid obstruction overhead. When ascending it could mean "stop here. this is my decompression ceiling" or "stop we are ascending too fast", or just generally "stop ascending at this depth".
  • Flat hand held roughly horizontal with tips of other flat hand's fingers touching the palm at right angles = "Time up" time to turn the dive and start heading back.
  • Arm held straight up at the surface = "Come and get me as soon as you can, but not an emergency"

Divers sometimes invent local signals for local situations, often to point out local wildlife. For example:

  • Both fists against sides of head: "I see a hammerhead shark".[3]
  • Fist with index and middle finger pointed out horizontally and alternately waggling up and down: "I see a lobster".[3]
  • Hand covering mouth, all fingers pointing outward from mouth and wiggling: "I see an octopus".

Other signals:

  • hand flat, fingers vertical, thumb against forehead or chest: shark.[3]
  • moving hand across torso in wave motion: current.
  • hands flat one on top of each other waving thumbs: turtle.[3]

Instructor signals:

  • point at diver(s) with forefinger, point at own eyes with forefinger and middle finger, point at own chest twith forefinger - "You (all) watch me" usually before demonstrating a skill.
  • gesture with open hand palm up towards student after a demonstration of a skill. "You try that now", or "do it again"

Torch / flashlight signals

The focused beam of a torch can be used for basic signalling as well.

  • Drawing a circle on the ground in front of buddy = the OK signal
  • Waving the torch up/down = attention please!
  • Rapid horizontal motion = emergency!

Normally a diver does not shine a torch / flashlight in another diver's eyes but directs the beam to his or her own hand signal.

Rope signals

These are generally used in conditions of low visibility where a diver is connected to another person, either another diver or a tender on the surface, by a rope. These date back to the time of the use of Standard diving dress. Some of these signals, or pre-arranged variants, can be used with a surface marker buoy. The diver pulls down on the buoy line to make the buoy bob in and equivalent pattern to the rope signal.

The British Sub-Aqua Club rope signals are:

  • 1 pull - are you OK? reply 1 pull - Yes I am OK
  • 2 pulls - Stay put reply 2 pulls - I am stationary
  • 3 pulls - Go down reply 3 pulls - I am going down
  • 4 pulls - Come up reply 3 pulls - I am coming up
  • 5 or more pulls - Emergency: bringing you to the surface or Emergency: bring me to the surface (no reply required)

Public Safety Divers

Public safety divers and many recreational divers use the following line signals while conducting circular and arc searches underwater.[citation needed]

Tender to diver

  • One pull on the line: okay, okay?
  • Two pulls: stop, take out slack, reverse direction
  • Three pulls: come to the surface
  • Four pulls: stop, don't move (there could be danger ahead or a boat entering the search area)

Diver to tender

  • One pull on the line: okay, okay?
  • Two pulls: advance line
  • Three pulls: object found
  • Four or more pulls: assistance needed

Commercial diving rope signals

Rope signals used in the UK include:[4]

Attendant to diver:

General signals:

  • 1 pull - Calling for attention, are you OK
  • 2 pulls - I am sending down a rope's end (or other pre-arranged item)
  • 3 pulls - You have come up too far, go back down till we stop you
  • 4 pulls - Come up
  • 4 pulls and 2 bells - Come to the surface immediately (often for surface decompression)
  • 4 pulls and 5 bells - Come up your safety float line

Direction signals:

  • 1 pull - search where you are
  • 2 bells - Go out along the jackstay or distance line, or straight out away from tender
  • 3 bells - Facing shot or tender, go right
  • 4 bells - Facing shot or tender, go left
  • 5 bells - come back towards shot or tender, or back along jackstay.

Diver to attendant:

General signals:

  • 1 pull - To call attention, or have completed the last instruction.
  • 2 pulls - Send down a rope's end or other pre-arranged atem
  • 3 pulls - I am going down
  • 4 pulls - I wish to come up
  • 4 pulls and 2 bells - Help me up
  • 5 or more pulls - Emergency, pull me up immediately
  • succession of 2 bells - I am fouled and need standby diver to assist
  • succession of 3 bells - I am fouled but can get clear without assistance
  • 4 pulls and 4 bells - I am trying to communicate on voice comms

Working signals:

  • 1 pull - Hold on or stop
  • 2 bells - Pull up
  • 3 bells - lower
  • 4 bells - Takeup slack on the lifeline or lifeline is too tight
  • 5 bells - Ihave found, started or completed the work

Cave line symbols

Cave arrows, Line arrows or Dorff markers (after Lewis Holtzendorff). These are plastic arrowhead markers which are hooked onto a cave line by wrapping the line around the arrow through the slots. They are used to indicate the direction to the exit, and can be identified by feel. The message is simple, but of critical importance, as if a diver does not know which way to go at a line junction there is a 50% chance of serious trouble. Line arrows are used at a junction on the permanent line, so when the diver gets back to the tie-off, he or she can identify which way to turn.

Miscellaneous emergency signals

A diver who has deployed a Delayed Surface Marker Buoy (DSMB) at the end of a dive may use a pre-arranged colour code to indicate if there is a problem. In some circles a yellow DSMB is considered an emergency signal, and red means OK. In most circles a second DSMB deployed on the same line will indicate a problem. A DSMB can also be used to carry up a slate with a message, but this is unlikely to be noticed unless a special arrangement has been made.

Diver down signals

  • International code flag "Alpha" (White hoist, blue swallowtail fly)
  • Diver down flag (Red with white diagonal)
  • Vertical line of "Red White Red" lights at night, vertical two red lights on encumbered side, vertical two green lights on clear side.
  • Vertical line of "Ball Diamond Ball" Day shapes


  1. ^ The Diving Supervisor’s Manual, First edition, 2000. The International Marine Contractors Association, London. www.imca-int.com ISBN: 1-903513-00-6
  2. ^ a b "Dive Links". http://www.dive-links.com/en/uwzeichen.php. Retrieved 2009-04-14. 
  3. ^ a b c d e f "Underwater Signals - UKDivers.net". http://www.ukdivers.net/comms/signals.htm. Retrieved 2009-04-14. 
  4. ^ Larn, R and Whistler, R. (1993): Commercial Diving Manual, David & Charles, Newton Abbott, ISBN 0 7153 0100 4

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