Sub Battle Simulator is a cross platform simulation of Submarine battles taking place during World War II. Featuring semi-3D graphics, and various views, it was one of the most ambitious simulators of any sort at the time of it's release (rivalling Flight Simulator II. You had to combat submarines, surface ships and aircraft, and there were multiple missions to choose from; in some you were on the Axis side, and others, the Allies. The map screenshot above is from one in the Pacific, near Indonesia. The simulation was quite complex and realistic, and made very good use of the 320x192x4 color mode.
One of the authors (Jesse Taylor) ended up porting several Epyx games to the Coco platform in the late 1980's (including Mind-Roll and Rad Warrior).
Title: Sub Battle Simulator
Author: Jesse Taylor & Mike Leber
Publisher: Epyx, sold through Tandy/Radio Shack
Released: 1987
Requires: Color Computer 1,2,3, 128K RAM, disk only, OS-9 Level II or NitrOS9, joystick optional.