But his exciting discovery may also raise questions about how deep world famous Loch Ness really is.
Britain’s deepest loch is Loch Morar, allegedly home to another elusive ‘water kelpie’ Morag at 1017 feet.
Previously, the UK’s second largest loch, Loch Ness, was measured at 813 feet deep.
But 43 year old tourist sightseeing vessel skipper Keith Stewart has found a crevice about nine miles east of Inverness and he has measured it with state of the art sonar equipment at 889 feet.
His colleagues in Jacobite Cruises, which operates sight seeing cruises down Loch Ness from Inverness, have now christened it ‘Keith’s Abyss’ and whetted his appetite to look for more mysteries the huge water expanse may harbour.
He said yesterday: “I wasn’t really a believer of the monster beforehand. But two weeks ago, I got a sonar image of what looked like a long object with a hump lying at the bottom. It wasn’t there when I scanned the loch bed later.
“That intrigued me and then I found this dark shape about half way between the Clansman Hotel and Drumnadrochit which transpired to be a crevice or trench. I measured it with our state of the art 3d equipment at 889 feet, which is 77 feet deeper than the previous recorded deepest point called Edwards’ Deep.
“I don’t yet know how long it is. But I have gone back several times over the abyss and I have verified my measurements. It gets deeper from 825 feet to the recorded depth.
“It is only about a few hundred yards offshore whereas previous sonar searches have traditionally been down the middle of the loch.
“Searches of the monster have also been in those areas as well as Urquhart Bay so maybe the local legends of underwater caves connecting Loch Ness to other lochs and perhaps even the water sof the east and west coast are true.
“Obviously it will need more research. But it is an intriguing prospect. It is possible that an underwater earthquake has opened this up in recent times because the Great Glen lies in a well known fault in the earth’s crust and tremors have been felt along it.
“I quit the sea and decided to look for something more sedate and being captain of the Jacobite vessle is something different and appealing to me.
“I started the job in March but now this discovery has made my job even more interesting.”
Gary Campbell, president of Loch Ness Monster Fan Club and Registrar of Sightings said: “This just adds another dimension - we thought the loch was 810 feet deep and just had a 20 foot diameter hole at the bottom. Now we’ve discovered a whole trench that makes the loch nearly 900 feet deep which is twice the depth of the North Sea.
“There could be more trenches which make it deeper. This looks like where Nessie and her whole family could really hide out and explain why they are rarely seen.
“Remember, Loch Ness is part of a huge earthquake fault line that runs from Canada to Norway. In 2013, there was a 2.4 magnitude quake in the loch - this was when Nessie disappeared for a whole year for the first time since 1925. It could be that this massive tremor opened up the trench giving the monster a new hiding place
“This now needs real research. No-one has done any real at the Loch for over 10 years. Lets get a submarine down to properly investigate the new monster trench.
“This summer we hope someone will come to the loch with the best detection sonar in the world to examine down to the depths just to see what is really at the bottom of the loch.”