if you want to shoot video from the tower, gopro IS NOT the right camera for you. It has a fisheye lens and anything farther than about 20' looks VERY far away.
I shot this pic of my 12 y/o last week with the gopro on my wakejak... and please note this is a heavily cropped image:
So the gopro on the tower really doesn't give you that great of a shot. On the transom for surfing is a completely different story. Or mounted to you or whatever. It's super versatile at getting shots from all sorts of crazy angles... but you just have to remember that you need to shoot the main subject 20' away or less.