Play proceeds like Hex (players alternate putting down white and black stones into the states). When the board is filled, the winner is the one who has formed a "Y" with his color. A Y must have beachfront property on all three oceans.
Give an informal proof that at the end of the game, there must be a Y.
Below is a picture of the dual graph of a specific game of Mudcrack Y. (Ignore the line around the whole thing.) The three acute corners are the boundaries between the three oceans.