The Sokei Regatta, also called the WK Regatta, is a race held in April between Waseda and Keio University. The first race between the two schools occurred in 1905, but the rivalry and tension started in 1933 at a Waseda Keio baseball game when an incident escalated into a riot of 6,000 people. Although not as well known world-wide as the famous Oxford vs. Cambridge and Harvard vs. Yale races, the Sokei Regatta attracts more than 30,000 spectators that line the Sumida River, and some call it one of the big three regattas in the world. 87 regattas have been held between the two schools in 113 years, with 17 getting cancelled (most during and after WWII). Due to river pollution, the race had to be relocated but was brought back to the Sumida River in 1978. The regatta has previously attracted elite crews such as Oxford, Cambridge, Sydney, and Melbourne. The women's eights race 1,000 meters and the men's eights race 3,750 meters. In 2018, Waseda won both the men's and women's eights race. This race course is close to the 2020 Olympic course in Tokyo Harbor (Hear The Boat Sing).