05/02/2010 05:12 am ET | Updated May 25, 2011

British Surfers Ride Wave Down River (VIDEO)

Surfers have made the most of a once-in-a-decade occurrence on the British river Severn by riding a tidal wave for miles.

The wave is caused by the funnel shape of the river, and occurs roughly once every ten years. Surfers traditionally compete to see who can stay on the wave for the farthest distance.

"It must be one of the toughest surfing challenges in the world because they key is to ride the wave for miles," Joanne Hillman of the British Surfing Association told the Times of London. "Most surfers would struggle to last the distance."