I use Canon HV40s as the main camera. They use miniDV tape and are essentially obsolete, but the quality is very good and the editing easy and you always have the tape as a backup. I use a "wide angle lens" ( Canon Wide-converter WD-H43, 43 mm base) most of the time, as it really makes a difference in the confines of a boat by widening the view.
Like everyone else, I also have a couple of GoPros. For the underwater shot, I just lowered the camera on a string down about 75 feet. I made a "platform" using a claw hammer and duct tape. What else to do when becalmed?
The wide angle, fixed-focus lens of the GoPro, attached to a stick, often makes the stick invisible. They have really changed the world.
You could easily video yourself doing your own appendectomy if the spirit moved you, and somebody probably already has.
A new GoPro, without a lot of mounts and brackets, is $200. Truly amazing.