Sonar pits two teams against each other in an underwater cat‑and‑mouse showdown, where the first side to deal two points of damage wins. Each match uses one of four map pairs, with each team receiving the same map in its own colour. The game supports 2‑4 players; teams of two split roles – Captain, who pilots the sub, and Radio Operator, who tracks the enemy’s moves. Solo players handle both roles.

On a turn the Captain announces an action: move the sub one space (north, south, east or west), use sonar, go silent, or fire a torpedo. Every move adds one energy to the ship’s register; other actions spend energy (sonar = 2, silent = 3, torpedo = 4). The opposing team’s Radio Operator records the path on a transparent sheet and, through deduction and trial‑and‑error, tries to pinpoint the enemy sub’s location. Sonar forces the opponent to reveal the row or column they occupy; Silent lets the captain move without gaining energy or disclosing direction; Torpedo lets the captain call out coordinates (e.g., F6) and deal a damage point if it hits. When a sub reaches the maximum of four energy, the captain must decide whether to keep moving, use sonar, or gamble on a torpedo, balancing risk and information.

A special action, “Surface,” lets the captain announce his current position, erase his previous trail and avoid getting trapped by his own line – crossing your own path is illegal. The game ends as soon as a team accumulates two damage points, granting an instant win. Sonar blends deduction, energy management and asynchronous teamwork, delivering quick (≈30‑minute) tense rounds that appeal to fans of light strategy, communication, and a suspenseful submarine vibe.