Underwater Hockey is a sport played between two teams of ten players. Six players per team are in the water, with four substitutes on the deck. Substitutions may be made at any point during the game. Positioning is similar to soccer with forwards and backs covering flexible "zones" around the puck. There is no goalie, and no offside rule. Unlike ice hockey, underwater hockey is a non-contact sport. Incidental contact is allowed, but charging, holding, obstructing, screening or handling the puck with the hand are illegal.

The puck weighs around three pounds, and is made out of lead with a bright plastic covering. Sticks are very short, around one foot long, and slightly hooked. The sticks are painted black or white and serve to distinguish the two teams. By flicking the wrist just right, the puck can be propelled along the entire length of the front edge of the stick and flung up to ten feet in an arc two feet off the bottom. Hitting the puck with anything other than the stick is illegal.

Ideally, the playing area consists of a pool 25 meters by 15 meters with a uniform depth of 2.4 meters (~8 feet) and a big tiled bottom. But in reality underwater Hockey is played in whichever swimming pool the team can find which might have a shallow end, a deep end, and a hill somewhere in between. At CSU we are happy to be able to play in two tiled bottom pools with a small depth difference.

Goals are located in the middle of the short end and are 3m (9') long. At CSU we just use two weighed cones to mark the goal posts, but more advanced goals are used in tournaments.

At the beginning of each point the puck is placed in the center of the pool, and both teams line up along the wall above the goal they defend. Each player must have one hand on the wall. With a shout of "sticks up... GO!" both teams race for the puck. Competition games consist of two halves, each 15 minutes long, with a 2 minute half-time for teams to swap ends. At CSU we generally scrimmage for an hour and a half, and stop the game sometimes to practice drills or discuss tactics.