first part,
it was a submarine based game similar to this but with updated graphics.
i believe it was made by the same pedople that went on to make the burnout games.

Second part, is it on gog.com or another service?

Deep Fighter? (by Criterion)

It's apparently not available anywhere to buy, as far as I know. The version I got to try worked fine with a few tweaks (using dgVoodoo, there was a bug with the mouse pointer but it may work fine with the latest version of this wrapper).

Other games in the same genre would be Archimedean Dynasty (on GOG), Aquanox series (on GOG, third game in development), SubCulture (no digital versions yet). You may also find Submarine Titans, but it's an RTS game.

Archimedean Dynasty ( aka Schleichfahrt ) would be my first guess too