It was an old Microprose title, I recall. You played a fighter-sub pilot operating out of a carrier submarine. A mercenary, I think. You had three regions to 'fly' in, and three subs to choose from, and unfortunately a set sequence of missions to complete. It wasn't perfect. But it was bloody atmospheric, I remember.
The deep ocean was suitably dark and gloomy; your little fighter had lights that you could illuminate the seabed with, and the seabed itself was complex enough terrain-wise that you could use it to evade pursuers or ambush prey... But you could go shallow, too, and even surface (although there was nothing to see once you got up there - the ocean surface was flat, with gentle Gouraud shades from light blue to slightly darker blue; no waves, or anything...).
I can't help but think what today's graphics technology could do with a game like that. Does anybody know of anything that's remotely similar? I don't necessarily mean in terms of fighting (I know there are a couple of arcadey-type sub games, but I'm more into simulation stuff), but even just flying around underwater and exploring in something a bit more manoeuvrable than a U-boat or an Akula class would be good... All the more so if it's got something to see on the surface, and the feel of abyssal depths beneath you...
I did try Virtual Sailor (v4, I think was my most recent), which at least lets you dive submersibles and the like, but I found it a little awkward control-wise as it's really designed for sailing boats. I'm just wondering if anyone knows of anything that might fit that rather vague bill, 'cos if no-one here does, then there's nothing to know of.