I used to have one of those, but sold it. I was told that they are either sub launched or air dropped to help facilitate communication between the sub and surface? I could be wrong.
You are right.
We used them to give info to submarine. But we stopped because they are too dangerous for frogmen and even submarines.
Sweet! Why are they dangerous? I never really understood their exact function, but assumed they were some type of relay radio?
No. This is an transmitter only, not a receiver.
It sends an accoustic wave and the waveform is very simple.
But the level is a lot too high and if dropped too close to the submarine it can dammage a lot of things.
Close to a frogmen it can kill him.
Do not forget : the water is not like air, it is uncompressible
Really interesting, I had no clue.