I want to shoot the following scene in amateur video: man jumps into the waterpool, swims under the water a couple of meters, and then floats back. The scene should be shot on head-mounted camera (which is inside a waterproof case).
The problem is I am not satisfied by the camera microphone sound. I would like to attach to man some other microphone (connected to audio recorder which is inside waterproof case in person's pocket). What microphone can I use for this case? Should it be some special waterproof mic?