Mr Edgley is no stranger to the cold waters surrounding the UK after he was the first person to swim around the island without touching land in 2018.
Having previously vowed to hang up his goggles after his Great British swim in 2018, Mr Edgley said he would do it again “for a really good cause”.
He takes the plunge on Wednesday and is also hoping to raise more awareness of the beauty and fragility of the sea forests beneath the oceans across the world as part of a partnership between Talisker & Parley For The Oceans.
“I just sort of went ‘you know what, I like it, I’ll get my goggles’,” he said.
"I’ll make a swimming spectacle of myself and we’ll try and raise awareness as much as we can – like David Attenborough said.”
His latest attempt to break the record for the longest ever tideless open-water swim, however, is “just another day at the office”.
The 36-year-old has gained almost a stone in weight by following a 10,000-calorie per day diet after arriving for training in Scotland a month ago.
He revealed he had been feasting on typical Scottish delicacies, including haggis and rowies – a savoury bread roll – to gain weight to keep him warm in the cool waters of Loch Ness.
He said: “I’ve been here a month now and I turned up 87kg and felt really good.
“I was lean, had a six pack and I was fast in the water. It was amazing.
“But I couldn’t stay in Loch Ness for much longer than a few hours.
“I was so lean. So the scientists at Loughborough uni, were like ‘Ross, you just need to get fat’.”
He asked the world’s strongest brothers Luke and Tom Stoltman, who live in Invergordon, for their expertise.
They have both won the World’s Strongest Man and Europe’s Strongest Man contest on numerous occasions.
Mr Edgley said: “They just said ‘oh, you need to put on fat. No problem. Come over here’.
“So I’ve been training and eating with them. They tuck away easily 10,000 calories. They took me to all of their favourite places to eat in Scotland. And we’ve just been eating haggis, rowies, everything.
“Now I’m 100kg. I put on 13kg in a month.”
Locals in Stonehaven have also been deep-frying Mars Bars for him and elderly women have been handing him bars of Scotland’s sugary favourite – tablet.
“This is why I love Scotland,” he said.
“I was doing the GB swim, and I came into Stonehaven, and they were just like ‘you’ve got to do 10,000 calories? No problem’.
“People deep fried chocolate. It was immense.
“I think there is something quite special about the Scottish diet I think and it’s so wholesome as well.”
Mr Edgley says the biggest challenge will be the unpredictable nature of Loch Ness. He said locals had warned him to expect typical Scottish weather – four seasons in an hour.
He said: “The water is just completely different because it’s obviously it’s so big, it just doesn’t get warm.”