Popular Ways of Underwater Communication for Divers

Last Updated: February 22, 2023

Having a greater variety of communication methods keeps divers safe in the water, allowing them to communicate with dive buddies, dive supervisors, and even other boats in the water.

Divers communicate underwater using:

  • Dive slates
  • Diving sign language
  • Verbal communication
  • Light signals
  • Line systems and tugs
  • Flags and buoys

Let me explore the importance of these methods and how they are used in a dive setting.

Why is Underwater Communication Essential to Divers?

If you have ever tried to speak underwater then you understand that verbal communication is not an effective way to get anyone’s attention (at least, not without appropriate gear). Instead, divers need to rely on a variety of additional methods for underwater communication.

These methods are the only way that divers can:

  • Convey potential hazards
  • Ask questions
  • Point out anything interesting

Divers have developed these methods of communication throughout the years so that anyone going underwater can communicate effectively and with urgency, keeping diving safer and even making the activity more fun.

What Makes Underwater Communication Difficult

When you dive you have many obstacles to overcome for effective communication.

With the regulator in your mouth, it is impossible to move your tongue, lips, and jaw as you normally would when speaking. Your mask blocks your nose, which also affects the quality of your communication.

Your gear can also be quite loud, especially the regulator that you depend on. Any bubbles in the area can be enough to make communication difficult.

On deeper dives, your breathing gas becomes denser. This changes the frequency of your voice, making it even more difficult to be loud enough to communicate through the water unaided.

While sound waves do travel underwater, the vibrations in your eardrums are different from what you experience on land.

All these issues pile on top of one another, and it becomes clear that developing non-verbal and modified methods of communication are essential for safe diving.

How Divers Communicate Underwater

Divers can use a variety of communication methods underwater, both verbal and non-verbal. Each of these methods should be cleared with their dive buddy and team on the boat to make sure everyone is on the same page.

Most divers do not rely on one method of communication. Instead, using a combination can increase what you are capable of communicating and make sure that any issues are noticed and dealt with promptly.

Divers should also be wary of any modifications they make to these systems. While coming up with your own ways to talk underwater with a regular diving buddy can be fun, they become obsolete if you dive with someone else or a different team.

Dive Slates

dive slates

A dive slate is a piece of plastic or PVC that you can write on underwater. These come in varieties from ones that are large enough for full sentences to smaller slates that can clip to your wrist. There are even dive notebooks comprised of multiple sheets of thin plastic.

Dive slates usually have a matte finish and you write on them using a wax pencil or other waterproof writing device. This allows you to easily erase anything you write on the board so you can reuse it throughout the dive. There are even pens and pencils that glow in the dark so you can convey messages this way in low light conditions.

While carrying another piece of equipment is not ideal, dive slates create an opportunity to write detailed sentences or ask questions. They can also be used to record data, keep a schedule, or draw a map so you can return to an area later.

You can learn more about dive slates here

Dive slates are the most effective tool for detailed communication underwater, so it is essential to make sure to secure them properly. While they are not expensive to replace, losing this method of communication to the depths of the ocean is less than ideal.

Diving Sign Language

underwater communication with hand signals

Using hand signals underwater is one of the easiest ways to communicate, and this method is widely accepted. While you can use hand signals specific to you and your dive buddy, understanding universal hand signals is essential for underwater communication with any team.

Some common things to communicate include:

  • Stop: face your palm to other party with all fingers vertical
  • Ascend: thumbs up
  • Descend: thumbs down
  • I’m okay (underwater): make an ‘O’ with index finger and thumb
  • I’m okay (by the surface at a distance): make an ‘O’ with both arms; if one arm is unavailable, use the free arm to make an ‘O’
  • Look: point to eyes and then to the direction intended
  • Something is wrong: open hands wide with fingers apart and palm pointed down; rock hand back and forth on the axis of forearms
  • Help: extend arm out horizontally; move up to vertical position; repeat
  • Danger: clench fist; extend arm and fist toward danger
  • Low on air: clench fist; move hand toward chest; repeat several times to indicate urgency

You can also use hand signals to identify specific hazards or animals in the water.

  • Boat: cupping hands together
  • Shark: take hands with fingers vertical; put them against your chest or head
  • Octopus: put the back of your hand to your mouth with your fingers open; wiggle fingers
  • Lobster: form fists with index and middle fingers pointed straight out; alternate moving hands up and down
  • Turtle: put hands flat on top of each other and wave your thumbs

You should be mindful of any unusual habits you develop when communicating with sign language underwater, and go over all these hand signals anytime you dive with someone new.

Related: Do Snorkelers Use Hand Signals?

Verbal Communication

There are two ways that divers can communicate verbally underwater.

Hard-wired communication is possible by using wires to connect the diver to the boat or even to other divers in the water. This requires speakers and microphones, and divers are limited to the length of the wire.

Divers can also use through-water methods that do not involve wires. These methods rely on ultrasound and radio waves underwater, and they come in push to talk (PTT) and voice-activated (VOX) varieties. Divers need to wear a receiver and a transmitter for two-way conversations.

Light Signals

Lights are not as effective underwater, but they do have their uses. Sunlight does not penetrate deep into the water, so you should be using underwater flashlights at any time.

These can be mounted or handheld, and you can shine them on your dive buddy to get their attention or turn them on and off rapidly.

Common ways to communicate with lights include:

  • Okay: turning light in a circular motion on the ocean floor
  • Danger ahead: moving light up and down
  • Emergency: moving the light side to side

Larger vessels must use proper light signals to indicate which side the diver is on. A red light will show which side other boats should avoid, while green lights indicate that side of the boat is free for approach.

Line Systems and Tugs

Line systems are one of the oldest methods of underwater communication, and they are often used as a backup now. There are several varieties in existence today, but each method requires the line to be free of slack.

The British Sub-Aqua Club, Royal Navy, and Commercial Divers use a similar set of five signals. Each signal has a specific number of pulls on the wire that allow communication between the diver and the boat.

A system used mostly in the United Kingdom and South Africa, incorporate bells on the line to enhance communication.

Flags and Buoys

flag and buoy when diving

Flags (diver down flags) and buoys can be used as a visual way to communicate where divers are in the water. Without these tools, other boats might run into the wires connecting the diver or even the diver.

Flags can also be used by smaller vessels that cannot use light to indicate which side of the boat divers are on.

Divers can use delayed surface marker buoys (DSMB) to indicate where they will be resurfacing. These are inflated under the water and released to float to the top. The dive team can then prepare to bring the diver aboard or to shore.

Final Thoughts

Divers need to rely on a variety of methods to communicate underwater in order to remain safe and stay in touch with their buddy or their team on the surface.

It could be as simple as writing a message on a piece of whiteboard or some light signals though your flashlight, or it could be as advanced as wireless voice-activated two-way conversations.

However, the most common method of communication underwater is sign language used between divers. It is almost universal and hand signals can be used by familiar divers and also by those who are complete strangers.

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