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. 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 in-play members of both teams are free to swim anywhere in the play area and try to score by manoeuvring the puck into the opponents' goal. Play continues until either a goal is scored and players return to their wall to start anew, or a break in play is signalled by a referee due to a foul, a time-out, or the end of the period of play. A typical playing formation is the 3-3 (three offensive players or forwards, and three defensive players or backs).

There are a number of penalties described in the official underwater hockey rules, ranging from use of the stick against something (or someone) other than the puck, playing or stopping the puck with something other than the stick, and "shepherding" (interposing one's self between a team-mate who possesses the puck and an opponent; one is allowed to play the puck, but not merely block opponents with one's body). If the penalty is minor, referees award an advantage puck - the team that committed the foul is pushed back 3 metres from the puck, while the other team gets free possession. For major penalties, such as a dangerous flick (e.g. at or near an opponent's head) or intentional or repeated fouls, the referees may eject players for a specified period of time or the remainder of the game. A defender committing a serious foul sufficiently close to his own goal may be penalized by the award of a penalty shot or a penalty goal to the fouled player's team. Games consist of two halves, typically ten to fifteen minutes in length and a short half time interval. At half time the two teams switch ends.