The photograph, which shows an object with three humps breaching the surface of the lake, is said to be the best evidence yet of what some claim is a monster lurking beneath the depths.
It was taken on a camera phone by Tom Pickles, 24, while kayaking on the lake as part of a team building exercise with his IT company, CapGemini, last Friday.
Mr Pickles said he saw an animal the size of three cars speed past him on the lake and watched it for about 20 seconds.
He said: “It was petrifying and we paddled back to the shore straight away. At first I thought it was a dog and then saw it was much bigger and moving really quickly at about 10mph.
“Each hump was moving in a rippling motion and it was swimming fast.