A former SAS soldier will attempt to solo row the North Atlantic, using the "sun and the stars" to find his way.
Ian Rivers, from Hereford, has turned down the use of a GPS system and says he will travel about 3,400 nautical miles between New York and the Scilly Isles using "natural navigation".
The veteran previously used nature as a guide after being kidnapped in Syria in 2013 – he successfully escaped, then navigated his way to safety using natural indicators.
Mr Rivers, who left the military in 2011, will use only a sextant and the stars to complete the Atlantic journey and is expecting to face "fierce" conditions.
"I wanted to make it a true adventure, going back to how people used to cross oceans 100 years ago," he said.
Mr Rivers will row for about seven hours each day and is hoping to set off on 20 May if the weather permits.
His 27-year military career began in 1984, during a basic training course with the Royal Artillery.
To this day, the veteran maintains that transitioning into the Armed Forces remains the hardest task he has faced.
A career with 29 Commando followed, before passing SAS selection in 1991.
Mr Rivers said two decades in the Special Forces took his "fitness levels" and "mental aptitude" to the next level.
Mr Rivers' time in the Armed Forces fuelled his passion for pure navigation – he became a trained mountain guide and ocean yacht-master, traversing all the major mountain ranges, deserts and oceans of the world.
He says isolation will rank as one of the toughest aspects of the Atlantic challenge, named Row Sentinel.
"I don't particularly like my own company. I prefer the company of other people," he said.
"So initially, after a week or so, I'll just get into the equilibrium of being on my own and getting into the routine."
The challenge is expected to last six weeks and the veteran will take enough food on board for 90 days, with extra rations and fishing rods just in case.
He is raising money for the Special Air Service Regimental Association and St Michael's Hospice in Hereford.