If you have ever thought about scuba diving, then you have probably either seen it in a movie or video and been intrigued by it. You probably have also seen in the videos that the divers cannot communicate through spoken language; they are obviously underwater and need to keep their mouthpieces in their mouths to breathe. So how do they go about communicating with each other then?

To communicate with other divers, scuba divers will mainly use a standardized set of different hand-signals and other visual aids. However, they can also use technology such as special radios to communicate with divers on the surface.

One of the most important aspects to learn when beginning to train for scuba diving is how to communicate with your dive buddy. This allows for a smooth dive and any communication for when trouble arises. This interactive guide is the most comprehensible guide that you can find when it comes to how scuba divers communicate. 

Diver Communication

Diver communication is all of the different ways a scuba diver can communicate. Divers usually dive with at least one other person, a diver buddy, and need the communication to indicate certain things, describe a situation, or request something. If a diver goes solo into the water, there are communication techniques they can use with their diving supervisor.

While communication techniques have improved over the years due to technology, water still prevents perfect communication between divers and their dive teams. Initially, wires were all that was used to communicate with someone in the water, but now things have progressed to using vocal communications. 

The reason water is such a hard element to communicate through is the fact that it reflects an image back at the viewer, making it hard to properly see beneath the surface. It also reflects most vocal attempts directed towards the under-surface from above which makes communications difficult. 

Diver Communication: History

The first form of communication used was a system of wires with a series of pulls determining different signals. The pulls were predetermined by the diver and their dive supervisor to communicate effectively. There are still emergency systems of the line pulls in place today with some divers, just in case all other forms of communications fail.

Electronic speaking tubes in the late 19th century were invented, tried, and failed. Early 20th-century diver telephones were successful and regularly used. They involved the communication wires being incorporated into the air lines with speakers and microphones inside the helmet of the diver. This allowed the diver to communicate directly with the “telephonist” on the surface. 

Eventually, with improvements, there became two-way communications between two divers underwater with similar wires, speakers, and microphones being used. The system is still in use today for some surface-divers who have full-face masks and lightweight demand helmets. 

Technology also allowed for “through-water” communications, which were developed by the United States Navy in the 1960s. Wires were no longer needed as divers could communicate using ultrasound techniques, thus allowing for more freedom of movement.

Types of Communication

Communication with divers is one of the most important requirements when it comes to scuba diving. Communications can indicate danger, a completed mission, or just simple heads-up. When divers go under the water, they have a few different options on how to communicate with each other and with their dive team on the surface. This is taught in scuba certification courses (11 reasons to get certified).

For communications with their fellow diver, the most common form of communicating is through hand-signals. The hand-signals that are taught at every beginner-level scuba diving class are generally universal throughout the diving community. They can be altered to fit each person or team, depending on preference. 

There is also a dive slate that divers can use with each other. This is essentially a whiteboard that functions underwater and allows messages to be written and shown to one another to determine how the other is doing, or which direction to proceed. 

Hard-wired communications are still very common today, with a majority of commercial divers using it. It is cheaper and more common than the through-water communications that bigger dive companies and militaries will use to communicate between divers and the dive teams.

Communications: Vocal

Vocal communications are the best way for a diver and his or her dive team to remain in contact with each other. It is the quickest and most efficient way for a signal to be communicated from one side or the other. 

There are two different types of vocal communications in scuba diving: hard-wired and through-water. Hard-wired is just as it sounds: wires being used to transmit vocal communications from the diver to the team and vice versa. Through-water communications are a bit more advanced, do not require wires, and have only become popular in the past 30 years or so.

Communications: Written

Most divers, when they go underwater, will have a dive buddy that accompanies them. The partnership is great for recognizing any dangers that may arise, and it can help in dire situations. While there are communication techniques that allow divers to talk to one another, those systems are generally expensive and not used by every diver.

A different form of communication used by divers is written communication. Writing underwater is a unique ability that scuba divers use, and they use a diver’s slate. Slates are great for writing short messages to the other diver. This allows for instant communication without too much confusion that could come from hand signals. Divers also use them to record data, keep a schedule, or draw a map to return to later.

The diver’s slate is a piece of hard plastic, usually with a matte finish. This allows divers to use a writing utensil, usually a standard lead pencil, and write messages on the piece of paper. 

The slate is either carried in a pocket by the diver or attached to their wrist. The pencil can be either attached to the slate itself or be attached to the diver’s wrist via a bungee cord. 

Scuba tablet communication

Communication: Nonverbal

While technology has allowed for the advancement of communication techniques in scuba diving, there are still tried and true methods that all divers must learn. Every scuba diving class or school that certifies new divers requires that the new divers pass a test and learn the hand signals. Like sign language, it is mostly universal, with a few variations that may fit the personal style of some divers.

Also, while underwater, scuba divers may also have flashlights on their person. These are also used to communicate with one another to signal different messages. 

And while divers are below the water’s surface, it is difficult to tell where they are. Thus, the use of flags and buoys to let other vessels in the nearby area that there is a diver in the water and that they should proceed with caution when traveling in the area. 

Also, used by boating vessels to let others in the area know where the diver potentially is, a series of lights. These lights can show which sides of the boat that are free to approach and which sides have divers near them to indicate that particular side is occupied. 

Finally, the oldest method in the scuba diving book: the line system. Still in place today, the system varies between country and to each personal diver and their team. But the system still has the same goal: communication with the diver.


The beginnings of hard-wired communications take place in the late 19th century. Scuba diving in those times required a massive helmet to be worn by the divers, with hoses attached to a pump on the surface, with someone literally pumping air into the helmet for the diver to breathe. In 1874, Louis Denayrouze patented a speaking tube system that would allow the diver to vocalize with their dive team on the surface.

The system Denayrouze used involved a second hose with a diaphragm being attached to the helmet. Unfortunately, the communication was faulty at best (the dive team would literally scream into the tube down to the diver to communicate). Soon after, electronic-power telephone systems were used to attempt communicating between the two parties.

This system used a series of wires connected to a base system on the surface that would allow the divers to communicate with their team (initially) and also with their dive buddy (invented later). The dual-communication between divers required an operator on the surface to relay the messages between the two divers, as direct communication between dive buddies was not yet capable. 

Later in the 20th century, diver telephones became the norm for scuba diver communications as technology advanced and allowed for better sound. The wires generally ran to the scuba diver, with speakers being placed inside the helmets. Microphones placed at the front of the helmet, or throat-mikes worn by divers, allowed for the divers to talk back to the surface team.

These systems are still in use today and are more common for use among commercial divers. There are even closed-circuit screens that allow the dive team to closely monitor the progress of the diver and their vital signs. This allows for quicker reaction times to any dangerous situations. 


The other form of vocal communications is called “through-water.” Instead of wires being needed and attached to a diver, through-water communications require no wires, with communication transmitted across radio waves and through ultrasound techniques. There are two types of through-water communication: acoustic and push-to-talk/voice-activated.

The U.S. Navy developed the through-water technique in the 1960s. The first attempt initially failed, as the company Sound Wave System went bankrupt in 1977. Sound Wave System had created the Wet Phone, which used voice-activated technology that was supposed to allow divers and his or her team to communicate directly without wires. 

As technology improved, the 1980s provided a new form of underwater communication that was used through single-sideband modulation. This essentially allowed divers to communicate through radio waves with their dive teams. Without the need for wires, divers were able to go further down and a greater distance than before. 

Acoustic through-water sound techniques are the most commonly used in the scuba diving community. The acoustic technique is great but can be limited as one-way communication. The audio signal from the surface team is transmitted to the diver via a transducer and allows the diver to hear the signal directly. 

Amplitude modulated and single sideband systems provide the diver with a two-way communication setup. Both of these setups require the diver to wear both a receiver and a transmitter on their suit to allow signals to be received and transmitted back to the dive team. 

Push-to-talk (PTT) and voice-activated (VOX) are two techniques that allow signals to be transmitted between divers. PTT allows divers to communicate only when necessary, and it saves on battery life as well. The diver simply pushes the button when they need to communicate.

Voice-activated systems are similar to push-to-talk but do not require a button. They are simply activated by the voice of the diver. The downside of this technique is that it requires more battery power, which could potentially run out. And, if the outside noise (i.e., animals, bubbles, breathing) is loud enough, then the voice activation system may automatically become active. 

Hand Signals     

The most common use of communication between two divers underwater is through hand signals. Used by recreational, commercial, and sometimes professional divers, hand signals have become the language of the waters for dive teams. For them to be effective, though, the signals must actually be seen by the other diver, which means the diver must first get the other’s attention.

If the water is dark or hard to see in, a flashlight is sometimes used to illuminate the hand of the diver giving the signal. If that does not work, then the diver can sometimes swim close enough to the other diver to feel what the diver is signaling through their hands. 

While American Sign Language (ASL) can be useful for divers, both parties would have to be familiar with it, plus there are some signals that can be difficult to perform with rigid gloves on and with divers potentially holding onto items.

For the most part, hand signals are easy to understand and interpret if you have never been introduced to them beforehand. But, the divers need to go through the signals pre-dive to reassure one another that they are using the same signals to mean the same message portrayed. 

Beginner divers are all supposed to be taught and tested on the most common hand signal uses. This list of signals was created by the Recreational Scuba Training Council (RSTC) and is to be learned by divers during instruction so that they may communicate effectively in training and eventually out in the water. 

Hand Signal Examples

The most common examples of hand signals used underwater are ones that someone has probably seen in a movie or video, or even ones they have used without even realizing.

  • OK Signal: This signal uses the index finger and the thumb to create an “o” with the other fingers extended. If a diver is wearing gloves and cannot extend their other fingers, simply creating the “o” is sufficient enough.
  • Ascending/Descending Signal: This is usually a thumbs up or down, depending on which direction the diver is indicating.
  • Something is Wrong Signal: This requires the hand to be flat and rock back and forth on the axis of the forearm. 
  • Stop Signal: This signal is obvious and used just about everywhere. It involves the hand to be open and vertical with the palm facing the receiver.
  • Boat Signal: The cupping of two hands together is the best way to signal this.
  • Out of Air Signal: Using a flat hand, a chopping or cutting motion across one’s throat indicates the diver is out of air in their tank.
  • Look Signal: This signal is performed by pointing to one’s own eyes and then in the direction intended. 

While this is not the complete list of hand signals between dive buddies, it gives a general glance at what divers use to communicate with each other. There are even more signals out there as well, even ones to indicate which animals that the diver might have either seen or come across previously. 

  • Shark: A diver will take their hand with their fingers vertical and put their thumb against their chest or head.
  • Turtle: The diver takes their two hands, flattens them on top of one another, and then waves their thumbs.
  • Octopus: The diver takes an open hand, with the back on the hand across their mouth, and wiggles their fingers.
  • Lobster: The diver will form fists, with the index and middle fingers pointed straight out, and alternate wagging their hands up and down. 


Flashlights are great tools for scuba divers to bring down with them underwater. They can illuminate dark caves and other hard-to-see places and show them to their dive buddies. Flashlights can also be used in emergencies for communicating with their fellow divers.

Generally, the signals are limited. One big use of the flashlight can be to illuminate the signal being given. Divers never shine the flashlight into the eyes of the other diver, and that could lead to a blinding sensation. 

Instead, they will use the flashlight to illuminate their hand and signal to their dive buddy. They can also use to gain the attention of the other diver. Plus, there are a few simple signals they can use with the flashlight.

A circular motion of the light can indicate the diver is “okay.” Pointing the flashlight in one direction or another can indicate which direction the diver wants to proceed to. Waving the flashlight side to side quickly can indicate that danger is close or that the diver is having an emergency.

Flags and Buoys

When a diver goes underwater, they can be attached via wires for breathing and communication. The surface team can either be on land or in a boat. Either way, flags, and buoys are two tools used by the dive teams to signal to people and other vessels in the area that there are divers in the water.

It is important to alert others about divers in the water because of several safety reasons. For one, boats should not venture too close to a boat that has a diver with wires, as the other vessel might damage or even cut the wires, leaving the diver in grave danger. It also signals that other boats should be on the lookout for any diver surfacing near the boat.

There are two versions of alerting other boats to a diver, called “diver down” flags: one is international, and one is common in the United States and Canada. Both flags serve the same purpose: alert others that there is a scuba diver in the water.

The International Flag, called the International Code of Signals (ICS) “Alpha” Flag

was put into place in 1972 by the International Regulations for Preventing Collisions at Sea and the United States Inland Navigation Rules. Essentially, the flag’s purpose is for smaller vessels who cannot illuminate the appropriate lights to show the vessel is limited in maneuverability because of a diver. 

The second flag is one more common in the United States and Canada. This flag was devised in 1957 and is more so flown when the diver is at a certain depth in the water, either going down or coming up towards the surface. The flag is also typically flown on the side of the boat closest to where the diver is, rather than the ICS Alpha Flag, which is just flown on the mast. 

Buoys are also used as signals for when divers are in the water. They are most commonly used with the red-and-white “diver down” flag, with the buoy in the water where the diver is close to the surface and the flag on top of the buoy. 

There are also delayed surface marker buoys (DSMB), which are used by the divers themselves. The buoys are inflated underwater and released to the surface, thus showing where the diver is going to resurface. This allows the surface team time to prepare for the diver to surface, and to bring him or her back onboard or to shore. 


If the vessel that is being used for diving is large enough, then the vessel must be illuminating the proper light signals to indicate which side of the vessel the diver is on. This is usually indicated by red lights showing which side(s) of the vessel that is not free and has a diver potentially on them. Green lights are used to show which side(s) of the vessel is clear and can be approached. 

Line System

The line system, or wire system, is the oldest and more commonly used form of communication between divers and their surface team. The system is still in use today by most divers, who really use as a backup system of communication, should their own wires stop working. The series of pulls can be traced back to the wires on a vessel or land, or even attached to surface buoys, with the number of times the buoy gets dunked indicating a signal.

There are numerous “languages” of wire signals from across the world; there’s the British Sub-Aqua Club, Public Safety Divers, Commercial Divers, the Royal Navy, and the U.S. Navy. Each version of the language requires the wires to be free of slack for the wire signals to come across clear and concise. If the signals do not, then the diver could be in trouble.

The British Sub-Aqua Club’s signals are few and are similar to the Royal Navy and the Commercial Divers signals. There are five signals, with the number of pulls on the wires indicating a message to the diver or from the diver. 

Some recreational divers, while conducting circular and arc searches, use the Public Safety Divers signals. There are four common signals used, each indicated by the number of pulls by the diver or the surface team. 

For the Commercial Divers, their system is mainly used in the United Kingdom and South Africa. This system is unique because instead of relying solely on a series of pulls, they also incorporate bells to further enhance the communication between the two parties. With the added use of bells, there is an expanded list of messages sent back and forth. Of note though, a single bell is never used as a signal, just in case there is an accidental snag of the wire by the diver. 


Scuba divers go into the water and enter a world of serenity that most people never get the chance to see. For the divers to remain safe, a series of signals is being used every day that allows divers the chance to communicate with their dive buddy and with their surface team watching from above. 

It could be as simple as a series of wires connected to the scuba helmet pulled to indicate a message, or it could be as advanced as wireless touch-to-talk activations that allow divers to communicate effectively. Of course, the most common form of communication is the hand signals used between dive buddies, as it is almost universal and can be used by familiar divers and ones who are complete strangers.