Maybe some sort of sound magnifying device?
A sound pistol (to scare off bity fishs)? Hm, could make sense. Does something like this exist? Anybody knows?
Under the water as soon as there is visibility, specially for the color, the lantern or torche is useful in cloudy waters like those of the Bay of Biscay. The torche would be used to see during the immersion, whereas the flash would be used solely to photograph.
So I think I customize it a little bit and add a yellow or white front so it can be recognized as a torch/flashlight.
maybe something like this one??
maybe something like this one??