Submarine!

Submarine! is a variation on Battleship. A submarine is hidden in a 100 by 100 grid. You can deploy a depth charge at any point in the grid. After the depth charge is destroyed the sonar equipment of your ship can detect the echo on the submarine and the distance of the submarine to the explosion. The submarine will try to move away, but it can only go up and right in the grid. Only a direct hit destroys the submarine. When hitting within five squares it counts as a minor hit. After four minor hits the submarine quickly speeds off to a new position where it is repaired. An updated version of the game restricts the submarine to the initial 100x100 grid and also gives a direction after each depth charge.