Castles by the Sea is a sandcastle building puzzle game for 1-4 players. As a group of small creatures called "beach dwellers", your goal is to build and populate a kingdom by the sea.

Each turn you place blocks and figures on the map to earn victory points. The core of the game resembles abstract strategy games like Santorini, where players must optimize three-dimensional placement on a shared board.

Hazards are the only source of randomness in the game, and even those depend on the players' choices. Each turn you must choose your placement carefully, optimizing your score while thwarting your opponents' plans.

The game ends after a fixed number of turns. Few castles will remain standing after a final assault from the perils, but the kingdom with the most sand dollars can claim victory.