The official rules of Underwater Hockey (UWH) are available on the website of the sport's international governing cody (CMAS) in two parts, Volume 1 - Playing Area Requirements and Volume 2 - Rules of Play.
UWH is a team sport, with each made up of 6 active players in the field of play, and up to 4 alternates available “on the fly” as substitute players. The teams are identified by the colors (blue/black vs white) of their one handed sticks and head covering (caps), and sometimes also by their swimsuits at major competitions. The teams work to push the puck into the goal at each end of the playing area (court).
While many teams practice and scrimmage in whichever pool is available to them a regulation court must meet specific length, width, and depth, requirements. Unlike other sports, the total playing area is only part of the equation, UWH has a total playing volume requirement, which is itself a range to allow for differences in pool construction.
A regulation game is two (2) 15 minute halves, with a three (3) minute half-time. Oftentimes smaller tournaments use a shortened version of the time requirements to fit more games in with typically only the finals and medal games being the full regulation time.
The heart of playing UWH is players are only allowed to interact with the puck, and they are only allowed to do so with their stick. Most of the player interaction rules stem from this concept. UWH rules have primary goals to ensure player safety and fair play, violating these rules is called a foul and each has specific penalties to be enforced. Understanding fouls and the protocols that occur after a rule violation is very important for players, coaches, and especially the referees.