Tsukishima Mizukake Matsuri
Tsukishima is one of the small island in Tokyo Bay. It is famous for its monjayaki street today.
Tsukishima in English mean the Island of the Moon, which is quite poetic, but it used to be a place for fishing in the past (it must be why it is called so as fishing occurs early morning, before the sun rises). And the gods (kami) of the island are protecting the fishermen. The tradition was for the fishermen to go into the sea with the Mikoshi, the mini-temple that holds the kami's spirit and that they walk around the area protected by the kami. It must have been a huge fun to splash in Tokyo sea, for the kami themselves and for the fishermen but today, it is not possible anymore. So, instead of jumping into the sea with the Mikoshi, evrybody throw water at them: children, adults, firemen...
It is a huge fun, and, sincerely, watching all these men, soaked in water, is a thrilling experience. Besides, it is also quite refreshing.
It happens in August, but every 3 years.