7. Underwater Hockey



A little known sport, underwater hockey is what some divers like to do during the winter months when the outside water is too cold for diving. The sport was invented in Great Britain during the 1950's when some British divers were looking for ways to stay fit during the winter.
 
The game is played using nothing more than snorkeling equipment - and of course the stick, protective gear and gloves - which adds breathing as an important game factor, meaning players have to manage the oxygen in their body. The game is played at the bottom of the pool using a puck weighing over one kilogram. The sport is tough and tiring though it is not as bad for experienced divers capable of holding their breath for extensive periods of time. The sport is becoming increasingly popular around the world and some countries have formed national teams which take part in world championships.

9. Slacklining



A balance sport, Slacklining utilizes nylon webbing stretched tight between two anchor points. It is distinct from tightrope walking in that the line is not held rigidly taut — it is instead dynamic, stretching and bouncing like a large rubber band. The line's tension can be adjusted to suit the performer and different types of dynamic webbing can be used to achieve a variety of feats. The line itself is flat, due to the nature of webbing, therefore keeping the slacker's footing from rolling as would be the case with an ordinary rope. The dynamic nature of the line allows for imposing tricks and stunts.
 
Christian Schou holds the Guinness World Record title for the highest slackline after crossins a Norwegian fjord in Kjerag, Norway at 3,280 feet (1000 meters) — the equivalent of 3 Eiffel towers high.