The game was invented in Great Britain in the 1950s by divers who wanted to stay in shape during the winter. You play underwater hockey without air tanks, only a snorkel, so you have to be good at holding your breath for a long time. The puck weighs over one kilogram, and you hit it with tiny sticks that sends it zooming along the bottom of the pool into your opponent's goal.
This video of the Singapore Underwater Hockey Club helps you see what's going on from the players' point of view.
http://www.yofavo.com/?p=557 - via darkroastedblend