Lehapanin I do not even know how to answer you correctly.
See how the first camera is of course a very specific option, but if you use it with a stub you will win very much (I have a camera + a stub + microphone). But I already own a prof. Photo appliance with a full matrix. Therefore, the action camera is used only for video, and only for fast shooting, because the quality from the camera will always be better. But in your situation, shooting in water = an action camera with or without a box depends on which camera you are.
If you take the usual digital video camera, you will win in the quality of shooting and the corners will be human, but it will not work in water.
A small conclusion: You can certainly use as the first camera, but the viewing angles are just space and shooting in the dark is sadness.
The sound, as for me - not a critical problem)
If there is a desire, find my posts, a few pages back, there are links there, the truth is that they scold you on YouTube, see how the camera works with the stub and with the microphone.
P.S. Friends, I tried the camera on the latest firmware with a buttonhole - the sound of course became sad. The locking is very strong. I set the sensitivity to low - it seems to be normal. Later accomplish your goal for sure.