Hi! I found your Submarines remake, and I've been searching for the exact same game from the Windows 95/98 era!
I remember the original having realistic-looking grey warships, from small patrol boats to frigates, cruisers and battleships. Larger ships had more depth charges but were easier targets.
There was a blue sky, an underwater grid, a visible seabed, and hidden submarines that could fire missiles at your ship once discovered. I also remember the sonar ping sounds.
I probably got it from an old shareware CD.
Have you ever managed to find the original game's name, or discovered any further clues?