In X Marks the Spot, players are pirates who aren't searching for treasure marked by an X, but rather trying to place that X themselves.

Each player starts the game with three gold(ish) doubloons and a hand of four cards; most cards are divided into two sections, with the sections indicating one of four pirate icons, open water, a ghost ship or a kraken. Some cards contain actions – e.g., cannon, plunder – that can be played against an opponent.

On a turn, a player draws two cards, then plays two cards. Cards are placed to form a grid on the playing area. A pirate icon can cover a pirate icon of the same type; a ghost ship is wild and counts as all pirate icons, and can cover and be covered by any pirate icon; open water can cover or be covered by any pirate icon or a ghost ship. A kraken can be covered only by a ghost ship, although a cannon can remove it from play.

Your goal is to create three Xs in the playing area that feature your secret icon. As soon as you (or an opponent) create an X, whether connected orthogonally or diagonally, you mark the center space with one of your doubloons. The first player to place her three doubloons on the board wins.