Sea Battle really deserves a higher grade than C-
Some people point to Utopia as being the first real-time strategy game, but Sea Battle came out earlier and Utopia is more turn-based.
Plus, what game from that period or earlier let your control so many varied units: Aircraft Carriers, Battleships, Destroyers, Submarines, PT Boats, Troop Transports, Mine Layers, and Mine Sweepers.
Truly ahead of its time.
The only drawback was that you couldn't play single player.