While swimming, I realized that communication underwater was very similar to the communication faced by deaf people. We are unable to hear what the other party wants to say. This led me to look at how divers do it underwater.
Based on the research and talking to a few friends who dive, it seems that they also use hand signals to communicate with each other underwater.
Most commonly used signs:
It is also the most commonly used form of underwater communication. There are an agreed-upon set of diving signs that can be used to quickly and easily communicate information in an emergency, and don’t require anything but the diver’s hands. These are limited by visibility, but even a novice diver should know how to signal to those around them that they require help and should be able to understand what other members of their diving group are signalling to them.
The difference between divers and deaf people is that communicating underwater is not as wide as living as a deaf person. A deaf person requires to sign a lot more than what a diver need for example, eating, drinking and other signs of everyday living as compared to just being underwater.
Other ways include:
Dive slate is another way divers communicate underwater. A typical dive slate is a piece of plastic, akin to a whiteboard, with a wax pencil/waterproof marker attached. These can be large enough to write full sentences on, or small enough to clip to a wrist. There are also magnetic variants, and even “dive notebooks” consisting of multiple sheets of thin plastic. Dive slates are important pieces of equipment to have, but issues arises when the slate is lost or visibility underwater is bad.
A transceiver. This is a wireless device that allows divers to communicate verbally, though speech won’t always be clear because of the nose plugs and regulators in the way. Some older systems are full face masks, while newer devices are much smaller and attach to the diver’s head via straps. These are a good first line of defense when it comes to underwater communication, but issues arises when a device fails or gets lost.