David Burns and Maghnus Collins will attempt to be the first people to finish the mammoth expedition for charity next month.
If successful, it would also be the longest verifiable swim ever completed in the Atlantic.
The intrepid duo have previously completed numerous man powered expeditions around the globe including a 250km run across the Sahara Desert, 25high altitude marathons in 26 days across the Tibetan Plateau, and Sand2Snow Adventures which raised in excess of €100,000 for charity
This time they will swim up to 12 hours per day in two six hour shifts, and aim to complete the challenge in just 100 days taking advantage of the slightly warmer summer water temperatures.
"Swimming as a means of covering long distances has been a largely unexplored field of human endurance and in attempting this circumnavigation we will be stepping somewhat into the unknown, this fact excites our whole team,” said David.
“We are proud of our adventuring track record and believe it was built on careful planning and dogged persistence.
"This will be our single greatest physical test and will hopefully conclude with an Irish team, supported by an Irish company completing the last great endurance challenge on this island."