The terrifying “beast”, thought to be up to 50ft long, was captured on camera by two pals out kayaking on Lake Windermere.
Shocked Tom Pickles and Sarah Harrington told how the mystery creature swept through the still waters at ten miles per hour – creating a giant wake.
They claimed they watched it for 20 seconds before it vanished into the mist, leaving them to scramble 360 yards to the safety of the bank.
Astonishingly, theirs is the EIGHTH sighting reported in the Lake District in just five years.
Last night experts hailed the snap as the best proof yet that “something” lives in Windermere which – at 10.5 miles long and 220ft deep – is England’s biggest natural lake.
And, referring to Scotland’s own legendary monster of the deep, one lake ecologist told The Sun: “If this thing is as big as they say it was, we’re in Loch Ness Monster territory.”
Graduate Tom, 24, snapped the creature on his mobile while on a team-building exercise with 23-year-old IT company colleague Sarah in Cumbria.
They were near the Lake’s Belle Isle when they saw the “monster” 160ft to the south.
Tom, based in Shrewsbury, said: “At first I thought it was a dog, then I saw it was much bigger and moving really fast.
“Each hump was moving in a rippling motion. I could tell it was far bigger underwater from the huge shadow around it. Its skin was dark black or browny and like a seal’s – but its shape was not like any animal I’ve ever seen.
“It looked about the length of three cars. It was petrifying.”
Sarah said: “It was like an enormous snake. It freaked us out. All I could think about was that I had to get off the lake.”
Locals in the town of Bowness have reported sightings of a creature, affectionately dubbed Bownessie, since the 1950s.
Among them is lecturer Steve Burnip, who claimed an encounter in 2006. He said yesterday: “What I saw shocked me. It had three humps – and the likeness with this is uncanny.”
Lake ecologist Dr Ian Winfield, of the Centre for Ecology & Hydrology, said the creature could be an Eastern European catfish – but he added: “If that size is accurate, I’ve no idea what it is.”
Yet sceptics remained unconvinced by the “beast” last night.
Nigel Wilkinson, director of Windermere Lake Cruises, said: “We carry millions of passengers and none has ever brought Bownessie to our attention.”