The Nikonos V is a darned nice toy. The 35mm lens is great. It is a viewfinder camera--no TTL focus, no rangefinder. Put 400 speed film in it, stop down, guess distances (there is a depth of field indication that is pretty useful) and it is pretty much a point-and-shoot.
There are only 2 lenses that work above water for the Nikonos--the 35mm and the 80 (or is it 85mm?). I have only seen the 80mm on store shelves.
Alternatives--the Hanimex Amphibian is one. Plastic. Point-and-shoot. Good down to 100' or more. I have pictures somewhere of my brother with a Hanimex diving the wrecks of Chuuk (Truk Lagoon). These go for ~$30 on eBay.
Now--what to look out for. Underwater cameras flood. Keep the O-rings clean and lightly greased. Use the correct grease (VOE--voice of experience).
Others--Sea and Sea, Minolta...good toys.
Below is a NikV shot as a P&S. I believe Kodak Portra, 35mm lens, f22, 1/200s, lab processed (if I recall). Your humble servant and his oldest boy, taken last summer.