Diver communications are the methods used by divers

Underwater diving

Underwater diving is the practice of going underwater, either with breathing apparatus or by breath-holding .Recreational diving is a popular activity...

 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
  Diving equipment
  Diving equipment is equipment used by underwater divers for the purpose of facilitating diving activities. This may be equipment primarily intended for this purpose, or equipment intended for other puprposes which is found to be suitable for diving use....
  
   such as full face diving mask
  Full face diving mask
  A full-face diving mask is a type of diving mask that seals the whole of the diver's face from the water and contains a mouthpiece or demand valve that provides the diver with breathing gas...
  
  s and diving helmet
  Diving helmet
  Diving helmets are worn mainly by professional divers engaged in surface supplied diving, though many models can be adapted for use with scuba equipment....
  
  s 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.
• Non-verbal communications:
• Hand signals - Recreational divers
  Recreational diving
  Recreational diving or sport diving is a type of diving that uses SCUBA equipment for the purpose of leisure and enjoyment. In some diving circles, the term "recreational diving" is used in contradistinction to "technical diving", a more demanding aspect of the sport which requires greater levels...
  
   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
  American Sign Language
  American Sign Language, or ASL, for a time also called Ameslan, is the dominant sign language of Deaf Americans, including deaf communities in the United States, in the English-speaking parts of Canada, and in some regions of Mexico...
  
   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 siren
  Siren
  In Greek mythology, the Sirens were three dangerous mermaid like creatures, portrayed as seductresses who lured nearby sailors with their enchanting music and voices to shipwreck on the rocky coast of their island. Roman poets placed them on an island called Sirenum scopuli...
  
  s, 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

Surface supplied diving

Surface supplied diving refers to divers using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel sometimes indirectly via a diving bell...

. 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.

Voice communication protocol

Underwater voice communication protocol is like radio communication protocol. The parties take turns to speak, use clear, short sentences, and indicate when they have finished, and whether a response is expected. Like radio, this is done to ensure that the message has a fair chance of being understood, and the speaker is not interrupted. When more than one recipient is possible, the caller will also identify the desired recipient by a call up message, and will also usually identify him/herself.

The surface caller should also give the diver a chance to temporarily suspend or slow down breathing, as breathing noise is often so loud that the message can not be heard over it.

Hand signals

Hand signals are a form of sign system

Sign language

A sign language is a language which, instead of acoustically conveyed sound patterns, uses visually transmitted sign patterns to convey meaning—simultaneously combining hand shapes, orientation and movement of the hands, arms or body, and facial expressions to fluidly express a speaker's...

 used by scuba divers to communicate when underwater.

The Recreational Scuba Training Council agencies have defined a set of hand signals intended for universal use, which are taught to diving students early in their entry level diving courses. The more commonly used hand signals provide the following information:

In most situations simple hand

Hand

A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...

 signals are used. The RSTC signals include:

• Emergency! Help me now: Waving one or both arms in a wide arc. Used on the surface.
• I'm OK: Touching or tapping the top of the head with elbow extended sideways: Used at a distance when the hand sign may be difficult to see.
• I'm OK: Forming a large circle with both hands above the head: Used at the surface as the OK hand sign can be difficult to see from a distance.
• I am cold! Hugging chest - Crossed arms in front of chest, upper arms grabbed by opposite hands.
• I am out of breath! Hands indicate rising and falling chest.
• I don't know: Shrugging shoulders, arms bent, hands to each side, palms up
• Danger in that direction: Pointing with a clenched fist.
• I can't clear this ear: Pointing at the ear with forefinger.
• Go that way: Fist with one hand, thumb extended and pointing in the direction indicated.
• Go under, over or around: With palm down, hand motion used to indicate intended route to go under, over or around an obstacle.

Other commonly used hand signals and variations

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

• The throat cut signal: "general danger" or "emergency".
• Tapping the mouthpiece: "I'm out of air".
• Pointing at the ear: "listen!"
• Hand cupped behind ear: "listen!"
• Repeatedly clenching and unclenching fist = "I have a cramp"
• 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).
• Index finger pointed up/down: "let's go up/down".
• Thumb up: "I am OK" (often with naval divers)
• 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"
• Moving hand across torso in wave motion = current.

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

• I see a hammerhead shark: Both fists against sides of head
• I see a lobster: Fist with index and middle finger pointed out horizontally and alternately waggling up and down
• I see an octopus: Back of hand or wrist covering mouth, all fingers pointing outward from mouth and wiggling
• I see a shark: Hand flat, fingers vertical, thumb against forehead or chest
• I see a turtle: Hands flat one on top of each other, palms down, waving thumbs up and down together

Instructor signals:

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

Torch / flashlight signals

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

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

Normally a diver does not shine a torch / flashlight in another diver's eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

s 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

Standard diving dress

A standard diving dress consists of a metallic diving helmet, an airline or hose from a surface supplied diving air pump, a canvas diving suit, diving knife and boots...

. 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 an 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 4 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.

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 and South Africa include the following:

Signals are combinations of pulls and bells, A pull is a relatively long steady tension on the line. Bells ar always given in pairs, or pairs followed by the remaining odd bell. They are short tugs, and a pair is separated by a short interval, with a longer interval to the next pair or the single bell. The technique and nomenclature derive from the customary sounding of the ships bell every half hour during the watches, which is also performed in pairs, with the odd bell last. One bell is not used as a diving signal as it is difficult to distinguish it from a jerk caused by temporarily snagging the line.

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.

Flags

• International code flag
  International maritime signal flags
  The system of international maritime signal flags is one system of flag signals representing individual letters of the alphabet in signals to or from ships...
  
   "Alpha" (White hoist, blue swallowtail fly)
• Diver down flag
  Diver down flag
  A diver down flag, or scuba flag, is a flag used on the water to indicate that there is a diver below. It is red with a white stripe from the upper left corner to the lower right corner, and was designed and introduced in 1956 by Ted Nixon of U.S. Divers, from an idea of Navy veteran Denzel James...
  
   (Red with white diagonal)
• Vertical line of "Red White Red" lights
  International Regulations for Preventing Collisions at Sea
  The International Regulations for Preventing Collisions at Sea 1972 are published by the International Maritime Organization , and set out, inter alia, the "rules of the road" or navigation rules to be followed by ships and other vessels at sea in order to prevent collisions between two or more...
  
   at night, vertical two red lights on encumbered side, vertical two green lights on clear side.
• Vertical line of "Ball Diamond Ball" Day shapes
  Day shapes
  Day Shapes are mast head signals indicating the navgation status of a vessel at sea to other vessels.The meanings of the shapes are defined by the International Regulations for Preventing Collisions at Sea.The most common signals are as follows:-...
  
  

Light and shape signals

A vessel restricted in her ability to manoeuvre, except a vessel engaged in mine-clearance operations, shall exhibit:

1. three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
2. three shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond;
3. when making way through the water, a masthead light or lights, sidelights and a sternlight, in addition to the lights prescribed in sub-paragraph 1;
4. when at anchor, in addition to the lights or shapes prescribed in sub-paragraphs 1 and 2, the light, lights or shape prescribed in Rule 30.

A vessel engaged in dredging or underwater operations, when restricted in her ability to manoeuvre, shall exhibit the lights and shapes prescribed in sub-paragraphs (1, 2 and 3 above) of this Rule and shall in addition, when an obstruction exists, exhibit:

1. two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists;
2. two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass;
3. when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shape prescribed in Rule 30.

Whenever the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in paragraph (above) of this Rule, the following shall be exhibited:

1. three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
2. a rigid replica of the International Code flag "A" not less than 1 metre (3.3 ft) in height. Measures shall be taken to ensure its all-round visibility.