The Nikonos V with 15mm lens and Fuji Velvia is easily capable of producing BETTER UW photos than digital. The 15mm was designed for UW and film still has a wider range of tones. It doesn't take that long to learn IF you take the time to learn exposure and depth of field principles. Get a good strobe(s), properly set hyper-focal for conditions, and you can concentrate on composition with the smallest, most agile rig on the boat.
If your focus was off you either need to learn to judge distances better or learn how to set hyper-focal focus. It's quite wide on the 15mm. However, although viewfinder parallax needs to be considered for close focus, the viewfinder is extremely easy to see through. The Nikonos 28mm is also a dedicated UW lens capable of exceptional results, although more difficult to use. I have a dedicated viewfinder for mine that is so rare I've never seen another or even a catalog listing for it. Is it the only piece of Nikon gear that never had a model number on it?
Yeah, it sucks to not have instant feedback and be limited to 36 exposures per dive. But, I still carry my Nikonos 5 when I want a small rig for strong currents, beach entries, or just to enjoy a dive for the sake of diving without concentrating on photography yet still have a camera along if I see something interesting. If I were you, I wouldn't hesitate to burn some film through that rig.