5 unusual world championships

They show up once a year during low tide at the mud flats near Brunsbüttel in northernmost Germany. Hundreds of mud lovers - known as "Wattleten" - gather at the mouth of the Elbe River for an unusual competition. This year, some 400 Wattleten are expected, along with thousands of spectators, for the annual "Wattolümpiade" - the mud Olympics.

The event incorporates a variety of sport disciplines, including mud soccer, mud handball, mud volleyball, and mud sled races.

The biggest difficulty is getting any traction in the knee-deep sludge, which often makes it look like the participants are moving in slow motion. But they have to hurry because they have just four hours before the tide shifts and the tidal banks are covered in water, ending the festivities.To make sure the matches stay on schedule, the refs will call a mud soccer game after just seven minutes, for example.

Another challenge is identifying the opposing team. After just a few seconds of play, and everyone is completely covered in mud from head to toe, with both teams looking the same.

Rumor has it that it takes days to get the sludge out of every crease, wrinkle and body cavity.

Dirty sports for a good cause

The best teams vie against each other in the final round for an eel relay. No, don't worry; they don't use an eel as a relay baton, but rather a rice-filled bicycle tube.

The Wattolümpiade was first held in 1978, though it started off as just a casual contest among friends. But when initiator Jens Rusch got cancer in the early 2000s, he stepped up the event, turning it into a cancer benefit for others in his situation.

Today, the Wattolümpiade and the Wattstock music festival that takes place at the same time continue to raise money for cancer patients.

Northern Germans, however, aren't the only ones to stage an unusual world championship. Click through the gallery above for some more crazy examples.