We need harpoons.
Make a mass driver sort of thing. Basiccally an underwater jetski. Stats, shoot spas minus speed with no damage. Minues speed should be around -2000 or even lower. It will basically shoot you miles forwards.
Underwater machinegun sort of thingy.
Starfish would be cool, but you already have a knife. How about a starfish launcher (spas) or maybe dual starfish (deagles)
Puking garble fish could be the M79 (don't search for a puking garble fish, it doesn't exist)
Some other gun could be a mussle which shoots pearls
The LAW should be something which shoots massive whales.
A shell could shoot crabs.