PSA: Water games already exist, and they are more fun than you think! Check out
Robosub and
MATE, for starters.
Team 842 will be competing in the Robosub competition for the 6th year in a row now. The team gets to go up against universities from around the world (Canada, Turkey, Russia, Japan, China, Singapore, India, Sweden...) in a week long pool-side competition on the beach of San Diego in the summer. Cheaper than FIRST, cash prizes, loads of career contacts, and you get to wear a swimsuit and play in the water.
Most top teams that compete in FRC can easily walk away with top finishes at these events. I'm not gonna take the hype for a water game seriously until you all start building some swimming robots!