Thrill seekers have described it as the ultimate log flume challenge. At 300ft tall and almost 1,150ft long, the Llyn Brianne Dam, near Llandovery, Mid Wales, is the tallest dam in Britain.
These images show a group of kayakers hurling themselves down the spillway at speeds of 40mph.
They drag their kayaks to the top before propelling themselves down the 1:3:6 gradient slope.
It takes just a matter of a few seconds for the kayaks to plunge to the bottom.
”They launched into the reservoir and went over the lip and down the spillway. It was bizarre to see someone shooting down this type of water. One of them went about 12 feet into the air when he hit a wave at the bottom. He landed upside down in the water.”