Imagine swimming the length of a 30-meter pool, numerous times, and treading water for four, eight-minute periods, all while not being allowed to touch the bottom or sides of the pool, and you have water polo. Water polo has been in the Olympics since 1900 for the men's competition, but only since 2000 for the women. Hungary is the all-time medal leader with 14, but the US is second with 10. The US women went home with the bronze in Athens, but the men haven't medaled since '88. Water polo is thought to be one of the most physically demanding Olympic sports, as players often swim up to 5km over the course of a match. The US Women are the favorites to take home the gold this year, and the men a long shot (18.5 to 1), with the Hungarians the favorites.