Hangzhou, China

Surfing China: Silver Dragon Hangzhou 2010 from Charles Lanceplaine on Vimeo.

Twice every year the Qiantang Tidal bore thunders down the river from the Hangzhou Bay almost 30 miles past the city of Hangzhou. Since 2007 Surfing China and Wabsono, with the permission of the Chinese government, has invited Pro surfers to surf the bore known as the "Silver Dragon". This year the team included Jamie Sterling, Mikala Jones, Robert Wingnut Weaver and Mary Osborne. Mary had the honor of being the first woman ever to have surfed the "Silver Dragon" and Wingnut, the honor of first "headstand".

Text from Vimeo. Found on 3.5 OUT OF 5 (dead link) while I was looking for blimp hangers.

Update: I thought the 'twice a year' bit was incorrect, I mean this wave is due to the incoming tide, and high tides happen twice a day. I had a hard time finding anyone to say otherwise. I think the deal is that due to some mysterious (celestial?) circumstances, you get an exceptional large wave twice a year. I finally found someone to confirm my suspicions on a site about the Bay of Fundy: "Tidal bores takes place twice a day during the flood tide and never during the ebb tide."

Update July 2018 replaced video embed code.