Here's a basic guide with the main information that you need to know to play underwater hockey:

Objective: The aim of the game is to maneuver a puck across the bottom of the pool and into the opposing team's goal using the stick. The team with the most goals at the end of the game wins.

Game Area and Time: The official dimensions of the game are 21 to 25 meters x 15 to 18 meters. The game has the duration of 2 parts of 15 minutes. Exist two areas for substitutions of players and a coach area.

Equipment’s: Each player needs a mask, snorkel and mouthguard, fins, a stick, a cap with ear protection and swimsuit with the player number. To play the teams need a puck and two goals with 3m of dimension in the bottom of the pool.

Teams: Two teams of 10 players. Each team with six players in the water at any given time, compete against each other. Four additional players wait on the bench.
Gameplay: The game begins with the puck placed in the center of the pool, and the two teams try to gain control of it. Players can swim in any direction, dive to recover the puck, and pass it to their teammates using the stick.

Referees: During a game exist 3 water referees, one chief referee on the deck. The referees communicate with hand signs, and the game is controlled by a buzzer to stop and start the game.

Infractions: Exist different infraction in the rules, including the use of the stick against something or someone other than the puck, playing or stopping the puck with something other than the stick, and "blocking". If the penalty is minor, referees award an advantage puck, where the team committing the foul is pushed back 3 meters (9.8 ft) from the puck, while the opposing team gets free possession. For major penalties such as a dangerous pass or intentional or repeated fouls, referees may expulse players for 1, 2 or 5 minutes, or even for the remainder of the game or tournament for very serious or deliberate fouls. If a defender commits a serious foul near their own goal, the fouled player's team may be awarded a penalty shot or even a penalty goal.

Strategy: A standard playing system is the 3-3, with three offensive players or forwards and three defensive players or backs. However, variations such as the 3-2-1 (three forwards, two midfielders, and one back), 2-3-1 (two forwards, three midfielders, and one back), 1-3-2, or 2-2-2 are also common. These formations are fluid and constantly evolving, with different national teams being proponents of tweaks in formations. Equally important to the formation strategy is the substitution strategy, as substitution errors can result in a foul or a tactical blunder.