The most famous waterpolo match in history is probably the 1956 Summer Olympics semi-final match between Hungary and the Soviet Union. As the athletes left for the games, the 1956 Hungarian revolution happened, and a 200,000 strong Soviet army crushed a small uprising of Hungarian insurgents. Many of the Hungarian athletes vowed never to return home, and felt their only means of fighting back was by victory in the pool. The confrontation was the most bloody and violent waterpolo game in history, in which the pool reputedly turned red from the blood spilt. The Hungarians defeated the Soviets 4-0 before the game was called off in the final minute to prevent angry Hungarians in the crowd reacting to Valentin Prokopov punching Ervin Zador's eye open. The Hungarians continued to win the championship by defeating Yugoslavia 2-1 in the final. Half of the Hungarian Olympic delegation defected after the games.

source: http://en.wikipedia.org/wiki/Waterpolo