My first PC Computer game was Epyx's Sub Battle Simulator:
This game was IBM PC Compatible with a whooping 4 color CGA capability!! Man-o-Man....a reason to upgrade from my Monochrome monitor!! Still have this 5'' floppy disked game on my library shelf.
'course, my first reason to love sub games was the Mattel Sonar Hunt game that I had when I was a kid:
Loved the capability of using the little "Periscopes" at the corners of the game to watch your buddy run into a mine as he moved over my side of the board searching for subs!
Hours of fun when you're 10 years old.