I thought this was one of the types that could be used both on the surface and underwater. Turns out it's just for surface use. No big deal... I should have researched a little more.
Tested it on the surface and it IS LOUD!!!
Definitely take the advice of one of the reviewers above and duck your head underwater while using it.
I don't keep it hooked up either. I have it in a butt-pack on my BP. If I need it, it's there.