Thanks for your comments @SPower and @danpost. I cannot test any game online (damn Chrome), That's why I give the code, to run it offline.

Looks cool! May I suggest a simple improvement: In your Fish class, instead of the line turn(90); put the lines: turn(180); getImage().mirrorVertically(); so your fish don't swim upside down.

Brian, I took your game and enhance it. No more errors and exceptions, Random location of computer ships. Validation of correct location of player ships. More ships, Win/Lose screens, sounds and images added. I don't know if I made it smarter, you be the judge of that. Thanks!