There are a lot of wacky extreme sports in this world ranging from boarding down volcanos to soccer on bicycles, but playing hockey under the frozen surface instead of above it? Now that, has got to top the list!

Originated in Austria, Underwater Ice Hockey also known as Sub-Aqua Ice Hockey, is just like regular hockey - except turned upside down. The games are played under a frozen lake about six meters wide and eight meters long. Players donned in wetsuits, flippers and special scuba masks, enter the freezing water from a small square hole that has been cut through the thick ice and, begin their pursuit of a floating Styrofoam puck.

While they don't have to know how to ice skate or run, they do have to be very good swimmers and most important of all be able hold their breath for long periods of time. That's because no oxygen masks are allowed in this extreme sport. Instead, players emerge from the hole about every 30 seconds to take a big gulp of fresh air, before returning back to the game. Since it is easy to get disoriented in the freezing water, four referees with breathing masks are present at all times, to guide players up to the hole, if they are unable to locate it themselves.

Each match is broken up into three ten-minute periods. At the end of each session, players are allowed a ten-minute break to come up to the surface and warm up from the freezing 2°C water. Fortunately, the fans that come to watch are not subjected to the same torture. They simply settle around the lake and watch the action from above - thanks to strategically placed underwater cameras, that transmit the game onto a screen.

As would be expected, this extreme sport, is currently popular that experience severe winter conditions - Like Austria, Finland, Czech Republic and Germany. However, judging from the interest from free divers, it is sure to catch on, in other parts of the world too.