Dolphin is a side-scrolling video game created by Matthew Hubbard for the Atari 2600 and released by Activision in 1983.
The player controls a dolphin attempting to flee from a giant squid. It must avoid colliding with packs of seahorses while navigating both forward- and backward-moving currents (indicated by arrows pointed with or against the dolphin's direction, respectively) which accelerate or decelerate its speed. Occasionally a seagull appears above the water's surface which, if touched, permits the player a short period of invincibility. During this time, the dolphin is able to touch the squid and drive it away.
The dolphin's sonar sounds to indicate how to avoid seahorses: a high pitch indicates an opening near the water's surface, and a lower resonance indicates a seafloor passage.