I did tests underwater with different combinations of settings and found these two to be best...
Wide 1080p 30fps - Makes the fish look smaller but drags all the scenery in, scenery can also a bit curved and forced in. But will have the widest view.
Medium 1080p 30fps - Gets everything you try to video into the view, you dont really miss any important stuff, looks natural and this fish look the size they should, perfect in My opinion!
I never used narrow underwater as it is really narrow and dont wanna miss anything! I always use Medium as is has the best perspective in my opinion.
If you dont do this i think you should start, just to keep your camera safe!
http://www.youtube.com/watch?v=vWf1cBweDfYAlso your camera would have less bobbing if its smaller! Where was my common sense.. aha