Tranquil Terror is a tile- sliding game where each diver must recover sunken treasure without being stung by the ever-shifting jellyfish. Players must make strategic decisions every turn as they try to find advantage using a limited action economy. Every turn repositions the tiles, and every action has ripple effects. Each player has a limited air supply that they must protect while maneuvering around the board. Players have the choice each turn for what actions to take. Actions include searching for treasure, shooing away a single Jellyfish, moving, expending air to shift an entire row of jellies, or recovering treasure. When players manage to recover a treasure in the game, they collect a physical treasure gem to add to their hoard. The key event comes every turn as an increasing number of tiles are added to one side of the play area, and slid across. The sliding tiles push the furthest tiles off the game play surface, thus rearranging the board. The tiles are chose at random, but placed carefully. If a jelly stings a diver, they lose air. As they lose air, the number of tiles being added each turn increases. In order to win, divers must recover 10 treasures first. However there is not always a winner. All players must search for treasure while keeping an eye on their air tank. If the air tank gauge reaches empty, their search is over.