Bad Bald Guy in Wet Suit Shoots Self at End With Spear Gun

by Josh
(Rochester, New York, USA)

In this '80s or early '90s film, a girl is in a canal or pool on an inflatable raft, and the bad guy who is bald and wears a wet suit swims underneath and essentially cuts her in half with a giant knife.

In another scene towards the end, the bad guy is in a shack and ends up shooting himself in the mouth with a spear gun.

What is this movie?