On his Odyssean journey, 25- year-old James Armour from Edinburgh completed the 191-mile route in 52 hours and 52 minutes on Sunday.
In total, he swam 20 miles, ran 52 miles and cycled 112 miles.
Mr Armour, a green technologies project manager told BBC Scotland it felt "unbelievable" to make history by being the first person to accomplish the achievement.
Beginning his challenge at the lighthouse on Barra Head, Mr Armour said: "There were enormous swells and my crew in a boat that was following me said at points I would disappear.”
"They were huge slow waves that would pick me up and take me down and I started to feel very nauseous.
"I tried to swim backstroke but I still felt awful. Then the tide turned as well and I was being pushed east away from my destination."
After starting his epic journey in the early hours of Friday, Mr Armour ended up swimming 2km further before he made it to dry land.
Talking about extreme seasickness which meant he was not able to eat, the 25-year-old said: "I felt so deflated that I felt so ill so near the beginning of the challenge,"
Despite this, his support crew who was following him throughout his journey via boat managed to get him travel sickness pills.
The seasick swimmer was able to slowly eat a few crisps, and then commence the swim to Vatersay.
Mr Armour’s route then saw him run 15.5 miles (25km) over Vatersay and Barra, before tackling a swim to Eriskay.
Not losing focus and keeping his athletic determination despite piercing northern winds, he cycled 62 miles (100km) to Berneray in North Uist.
He then swam 10km through the Sound of Harris – a channel between the islands of Harris and North Uist.
"The waves were dancing in the light that was coming through the clouds. There were huge white tips and it looked menacing," Mr Armour said after facing his most soul crushing point when he looked out at the choppy sea.
"I felt absolutely dead, I had no energy left to keep warm and I thought there was no way I could get across and that I was going to fail.
"That's when I shed a tear. I felt so empty."
By this point, Mr Armour’s tongue had also inflated as a result of the constant salt water rushing in and out of his mouth.
He said: "My tongue was so swollen I couldn't talk.
"The salt felt like shrapnel and I had scars all up my ribs from where my vest was cutting and rubbing under my wetsuit.
"It was very tough."
Other challenges came from angry aquatic life.
On his swim to Pabbay, in the daylight, roughly 60 seals charged towards Mr Armour.
He said: "I got a fright. I could see silver flashes under me and then one big grey seal came right up to me from below and stared at me with one eyeball very close.
"My support crew member said he was scared in the kayak as the seals were knocking his kayak."