(CNN) -- It's like a stunt from the latest James Bond movie, only this isn't a movie.
Adorned in a designer suit and sunglasses, a sailor sprints up the 30-meter mast of a boat as it plows ahead at a 60-degree angle.
Hopping over ropes and rigging it takes him just 16 seconds to reach the mast's peak. There, he checks himself, removes his sunglasses, pops them in his top pocket and dives into the ocean nine meters below him.
"It's the most stupid thing I've ever done," is Alex Thomson's frank assessment of his stunt.
"It wasn't safe at all," adds the yachtsman more used to solo circumnavigating the globe. "Only looking back do I really appreciate how dangerous it actually was."
The stunt was carried out without a harness, just a water resistant suit, although the risk was reduced thanks to the work of a stunt co-ordinator and two days of preparation on the water.
For Thomson's daredevil performance to succeed he also needed a wind speed of exactly 18 to 20 knots and for the boat to be traveling at 10 knots (a little under 20 kph).
The 37-year-old and his team began their search for the perfect wind speed in Palma, Mallorca, but were forced to switch to Tarifa in southern Spain because conditions weren't right before eventually shifting to Cadiz where the stunt was eventually performed.
"At the end of the first day, I had to sit down on shore and calm down," says Thomson.
"I was appreciating perhaps it wasn't safe at all, and there were some hairy moments when we were practicing. I remember one time I was halfway up when the boat suddenly tacked and I was just left hanging from the mast.
"Obviously falling from that height from the mast onto the deck isn't advisable," he quips. "The ramifications wouldn't have been great."
On the day itself, with stunning skies above, the stunt went pretty much perfectly, which had a lot to do with the man driving the boat, Ross Daniel.
"His was the harder, more nerve wracking job as he had to keep the boat just right," says Thomson. "Ross works for me and he's a good mate so obviously he was conscious he didn't want things to go wrong.
"I'm not sure if he was relieved come the end of it but he was certainly happy man with how it went."
As for Thomson's starring role in the escapade, he's conscious that he came very close to really hurting himself.
"Now the top of a mast isn't really designed for a man to dive off but I went for it and it held up," says the yachtsman.
"As for the dive itself, I slightly over-egged. There was some quite impressive editing work on that as I landed head first very close to my back.
"It was quite close to a back belly flop and, while I wouldn't have killed myself, I certainly would have had some nasty internal injuries.
"Diving wise, I'd always wanted to dive but wasn't sure until I got to the top whether I'd have the guts to do it.
"I'd been up a 10-meter board at a pool in training but never dived off it. So this was a first and, once I was up there, I sort of thought I might as well go for it."
As he pondered that stomach-churning dive, Thomson says he felt surprisingly calm.
"As a sailor I'm used to hoisting myself up the mast and you get well versed at reading the wind and the waves so I was quite aware if there was suddenly going to be a change in the boat's course," he explains.
There wasn't, he duly hit the water and quickly returned to the surface to the relief and cheers of his team.
Even now, Thomson, who has a penchant for being something of a daredevil, is not entirely sure why he performed the stunt.
"I did a keel walk a while ago and we did a video for that, which got over two million people watching which I was flabbergasted by," he admits.
"So we got talking about doing something else and this seemed a bit of fun really.
"I'd taken to running up the mast -- although not necessarily to the top -- for a while, mostly when entertaining people on the boat to, say, take pictures of them on the deck.
"So, going the whole way up and jumping off seemed a good idea.
"It's a bit like the Vendee Globe (the race to circumnavigate the globe). You sort of agree to it not thinking it will necessarily happen, and then suddenly the day comes for it."
Having done a keel walk two years ago and now a mast walk, Thomson is at a loss to consider what might complete a hat-trick of sailing stunts.
"That was the same after the keel walk. I'd never planned to follow that or do something like this, it just happened. So when I'm asked what I might do next, I literally have no idea."