How Do Divers Communicate Underwater?

descend with buddy

Unless you’re doing a solo dive, you’re going to be diving with one or two dive buddies and communicating between them is crucial for everyone’s safety. On the boat you’ll be able to converse normally and discuss different ways to communicate, the most common of which are hand signals, dive slates, or using a dive light.

You might be wondering if it is possible for divers to speak underwater. Sound waves travel 500% faster in water than air. The main issue is that sound waves are not perceived the same way underwater compared to land. Your inner ear will hear a different vibration which will make the words sound distorted. However, there are many ways to communicate underwater, and yes, there is a way to speak clearly underwater as well.

Why underwater communication is crucial

You will never take talking for granted once you go underwater and lose your ability to speak, so to speak. When you are first starting out, it can be frustrating not being able to perfectly communicate what you want to say. You have to rely on imperfect or delayed forms of communication such as hand signals, writing on a dive slate, or shining your dive light. Yet, even imperfect communication methods are essential.

Even with just basic hand signals, for instance, you can convey potential hazards to your dive buddies that can help everyone avoid a serious injury. Or if you are running low on air, you can signal to your buddy that you would like to use some of his or her air. When you are exploring and want to go a certain direction, you can let your dive buddy know so that he or she can follow you.

Underwater communication can also help improve the fun factor of a dive. You or your buddy can notify each other of the presence of marine life. For instance, you may see a shark, manta ray, or sea turtle in the distance and want your buddy to see it too.

While diving, it’s important to give your buddy a heads-up if a shark is coming so they won’t pee in their wetsuits when they turn their head to see a shark next to them. Maybe you can have a drink with your buddy later and talk all about how cool it is to swim with these majestic sea creatures or any other exciting things that happened during the dive.

To sum this section up, underwater communication makes diving safer and more enjoyable. If you cannot communicate with your buddy, especially if your “buddy” is a close friend or loved one, then you miss out on the shared experience of being part of something amazing together.

It’s also much safer to give each other a heads-up about potential incoming dangers. For this reason and more, you should be comfortable with at least one method of underwater communication.

Hand signals

One of the easiest ways to communicate underwater is with hand signals. The World Recreational Scuba Training Council (WRSTC) has created a PDF with photos of universal hand signals divers should use. With these hand gestures, you can silently and quickly convey information to your dive buddy.

The following are the most common hand signals used by divers (you can find all of these more in the PDF linked above):

  • Stop: Face your palm to the receiver with all fingers pointed vertically. Same meaning and hand positioning as on land.
  • Thumbs up: In the diving world, a thumbs up means you want to ascend, not that you did a good job.
  • Thumbs down: You want to descend.
  • OK (underwater): Make an “O” shape with your index and thumb by touching the tips together and extend the remaining three fingers. This is the classic OK hand signal that means you are okay or to indicate agreement. If you are wearing thick gloves then face the palm of your hand upwards, make an “O” with your index finger and thumb, and the three remaining fingers should be next to the index finger and bend in a similar position.
  • OK (by the surface at a distance): Have you ever done the YMCA dance? Similar concept here. Use your arms to form an “O” shape above your head. If one arm is encumbered, then with your free arm, touch the top of your head with the tips of your fingers while trying to make a large “O” shape.
  • Something is wrong. Open your hand wide, fingers apart, with your palm pointing down, rock your hand back and forth on the axis of your forearm.
  • Help. Extend your arm out to your side horizontally and move your arm to a vertical position, waving between these two positions.
  • Low on air. Make a clenched fist and move your hand toward your chest; repeat the motion several times to indicate urgency.
  • Danger. Clench your fist and extend your arm and fist towards the danger.

We’ve only just scratched the surface of the various gestures. You can learn all of these hand gestures and more by reading the PDF linked above or by taking the Open Water Diver course.

Different hand signal meanings

If you dive frequently with a buddy, be wary of developing new hand signals. While this may benefit you when diving with that buddy, it may serve to confuse you when you dive with others in the future. Be cognizant of any unusual signalling habits you might have so that you don’t confuse a new dive buddy.

Before a dive, especially if you are diving with someone you’ve never dived with, go over the hand signals you will be using and make sure that you are on the same page when it comes to the meaning of each gesture. Depending on where you are in the world, there may be some slight differences.

Dive slate

Another method of communication is to use a dive slate. The concept is basically the same as writing a message on a piece of paper on land, but underwater, you use an erasable board called a dive slate to write messages. If you want to convey complicated information or want to ask a question, you can just write it down on the dive slate. You have to make sure your buddy notices you pointing the dive slate in his or her direction, however.

You can’t use any pen to write on a dive slate underwater. You specifically need a waterproof pen. Dive slates solve this problem with their waterproof design. They are constructed from plastic or PVC and provide a waterproof erasable marker or pencil to use on the slate. Recent innovations are glow-in-the-dark markers or pencils that let you produce readable messages in the dark.

One downside of using the dive slate is that you have to bring extra equipment. You also run the risk of dropping the dive slate or pencil if it’s not properly secured on your gear. However, if you’re looking for a relatively cheap and straightforward way to communicate underwater, the dive slate gets the job done. Just make sure you don’t drop it, because it’s going to be lost forever in the depths if it falls.


Dive lights are not as effective as a dive slate or hand signals for communication, but they have their uses. A dive light is a special type of underwater flashlight that can be mounted or held in your hand to illuminate your environment. It’s essential if you are heading out into the water at night, but even during the day, it is very useful if you are diving deep because the sunlight does not penetrate very far into the water. They can also be used for communication.

Here are some common light signals you can use:

  • OK: Move the light in a circular motion on the ocean floor to indicate you are okay.
  • Danger: Move the light up and down to signal danger ahead.
  • Emergency: Move the light side to side to signal an emergency.

You can also shine your light on your dive buddy (try not to blind them) or turn your light on and off rapidly to get their attention.

Rope Tugs

You can’t communicate with your dive buddies using this method, but you can signal to the boat operator or tender. If the boat operator pulls on the rope once, he or she is asking if you’re okay. If you pull the rope once, you are responding that you are okay.

If the boat operator pulls the rope twice, he or she is telling you to remain where you are. If you tug the rope twice, then you are saying that you are staying where you are.

Voice System

There are full-face dive masks with voice systems embedded in them that allow you to talk to your dive buddies underwater, as if you were on the boat or on land. The system consists of a microphone and speaker. The microphone will pick up what you say and relay it to your buddy through his speaker, and he can do the same to you. There are two types of voice systems: hardwired and through-water.


Hardwired voice systems, as the name suggests, rely on using long wires that run to the scuba diver. The speakers are placed inside the helmets, and the microphones are placed either at the front of the helmet or the diver wears throat-mics. This allowed divers to communicate with the surface team by speaking.

This method was developed in the late 20th century and is still used today by commercial divers. Nowadays, there are even closed-circuit screens that let the dive team closely monitor the diver’s vital signs and progress underwater. This lets the surface team warn the diver if their vitals are changing.


The other method of underwater vocal communication is called “through-water”. Instead of needing long wires to be attached to a diver, through-water communication relies on radio waves and ultrasound techniques. Think of this as a walkie-talkie radio that is used underwater.

Unfortunately, there are some issues with this system, namely that the speech is hard to understand because the regulator is still in the diver’s mouth. For this to work well for recreational diving, the diver must be wearing a full-face mask so they can speak freely.

Why is it so hard to talk underwater?

When you’re scuba diving, you have many impediments to speech. You cannot move your tongue, lips, and jaw as normal since there is a regulator in your mouth. Furthermore, the mask nose blocks your nose, which also affects your ability to speak. Try pinching your nose and speaking and you’ll sound comically nasally.

Now try talking with your nose pinched and without moving your mouth and it’ll sound like you’re making unintelligible caveman grunting noises. Furthermore, even though sound travels well underwater, the vibrations in your eardrums are different than on land, so what you hear will sound different.

There is also the practical issue of sounding loud enough to overcome the loud noises from the regulator and bubbles that you and your dive buddy produces. Lastly, the deeper you are, the denser the breathing gas gets, and this changes the frequency of your voice, making it sound higher than usual.

Can other divers understand you when talking underwater?

We gave some reasons for why it is so difficult to talk underwater, but perhaps it’s still possible for others to understand you. First, you will need to be pretty close to your dive buddy. Second, you will need to talk slowly and loudly. If your dive buddy is familiar with your speaking style, he can fill in any gaps using context.

Even if the actual words are not understood, it is possible to understand the message based on speech volume, pattern, inflection, and non-verbal communication (e.g. looking at your body movements). With that said, it’s not recommended to talk underwater because the effort will cause you to waste a lot of gas.

Thus, it’s better to just rely on the more traditional underwater communication methods, such as hand signals, to allow for a more quiet and enjoyable underwater experience where you don’t sound like a grunting caveman.