In the initial OWD course, we already learn basic communication signals. “Are you ok?”, “Everything ok”,” I have problems”, ”I have little air and I need air”. They are usually complemented by other signs, but in the end, these are the important ones when you start diving. When through experience or training you become an advanced diver, you do dives that require more complex communication.
An advanced diver does deeper dives and has to be more precise in indicating the gas remaining in his tank. For this, many advanced divers use the signals used in technical diving indicating the pressure of the tank by numbers using the fingers of one hand. With the palm of the hand facing out and the fingers pointing upwards, to indicate from 1 to 5, and with the palm of the hand facing in and the fingers pointing to the side, to indicate from 6 to 9. The 0 is indicated by making a complete circle with fingers and thumb. This allows you to indicate to your dive buddy the exact amount of air or gas you have left in the tank. This system is also used to indicate depth or time.
There is a set of internationally standardized signs that with small variations are often used in technical diving that come from cave diving. Gestures and manual signals are also used to indicate things like “sediment”, “I have reached my return pressure”, “guideline”, etc…