Just like the childhood game Battleship, students aim to sink eachother's ships but while using vocab words. Rules are lined out for kids not familiar with the game. I teach Korean Elementary students who never heard of the game but fell in love with it once we got through the rules.
Words can be penned in before copies are made to make sure all of the boards are the same. Students can also pen in words as long as they make sure their team-mates use the same order of words.
Students can play in groups or 1-1. My students like to play 2-2 but keep 4 separate boards to allow for more ships.