SeaPup

In 1982, an ultra compact submarine was designed. Code name: Sea Pup. Information about this submarine is sparse and was never released to the public. There are currently no known records of its existence but many have since claimed to be part of the design or operation. According to those involved, it carries a much smaller crew and has the ability to launch four torpedoes in quick succession.

Gameplay:

Destroy as many ships as possible to get the highest score. The slower ships are worth 10 points, the medium speed ships are worth 30 points, and the fastest ship is worth 70 points.

After 400 points are scored 15 seconds will be added to the timer.

Source: TheGamesDB