Underwater hockey (UWH; also called Octopush and Water Hockey) is a global non-contact sport in which two teams compete to maneuver a puck across the bottom of a swimming pool into goals.

Two teams of up to ten players compete, with six players on each team in play at once. The remaining four players are continually substituted into play from a substitution area, which may be on deck or in the water outside the playing area, depending on tournament rules.

Before the start of play the puck is placed in the middle of the pool, and the players wait in the water, touching the wall above the goals they are defending. At the start-of-play signal (usually a buzzer or a gong), in-play members of both teams are free to swim anywhere in the play area and try to score by maneuvring the puck into the opponents' goal. Players hold their breath as they dive to the bottom of the pool (a form of dynamic apnoea, as in free-diving). Play continues until either a goal is scored, and players return to their wall to start a new point, or a break in play is signalled by a referee (whether due to a foul, a time-out, or the end of the period of play).