The Tor Dearg - the boat that is accompanying Henry O'Donnell on his voyage around Ireland - is docked at the port of Greencastle in Co Donegal, where I have arranged to meet the former Army Ranger.
The day is murky and the sea - all greys and muted greens - is not particularly inviting- looking. A storm is forecast, and Henry has already put in several hours of swimming by the time we meet. The previous day, he swam for 12 miles off the coast of Inishowen, braving the swells of the Atlantic Ocean. Stroke after stroke, it will be many miles before he completes his challenge.
Last month, he left his native Carrickfinn in Co Donegal to begin his epic odyssey circumnavigating the country by swimming with fins and a snorkel. Only a few weeks in, and he's had more adventures than most of us have in a lifetime. In the earliest days of the trip, he encountered four blue sharks, each the length of your average-size car, off Tory Island. He swam with dolphins near Culdaff and came across basking sharks off Malin Head.
As a sea swimmer, I've encountered the odd inquisitive seal, but I'm not sure how I'd handle something the size of a car cruising past me. I hope that I won't be too far out of my depth in going for a swim with the 56-year-old father-of-six, who believes he's been in training for this expedition from the time he learned to swim as a four-year-old.
Raised on a small coastal farm, Henry was one of 10 children. His early life was about working hard and nothing was wasted. The family harvested seaweed and his father, Peter, who died in 1993, did everything from farming to building.
At four years old, he watched his older brothers swim. He soon followed them. As he got older, he adopted a pet seal, which allowed him to feed it. He observed its movement in the ocean, trying to replicate its grace in the water.
"The seeds for this expedition were sown when I first went into the water in Carrickfinn. I learned how the seal moved in water and how it propelled itself. There's nothing in Irish waters that fazes me. I think I fit in with nature," says Henry.
The expedition, which will take many months, is to raise money for two charities - the Irish Cancer Society and Water Safety Ireland. Both are close to his heart. His younger sister Rose is a cancer survivor. Growing up in a coastal community, he knows the sea can be cruel and lives can be lost. He'd love it if he could raise a million euro for his chosen charities.
Safety is paramount on an expedition as vast as the one he is undertaking, and logistical preparation and forward planning for each trip leave no stone unturned.
The plan was to go on the expedition next year but when coronavirus hit, Henry's work as a security consultant for the corporate sector was seriously affected and he decided to bring the start date forward.
As well as undertaking lengthy swim training, he has also done sleep-deprivation and sleep-disruption training. Being ready to swim with the tide is important, and this might mean being up and ready to swim in the wee, small hours of the morning. Both he and all the crew conducted extensive safety and rescue drills. Nothing was left to chance.
Pushing himself to extremes means being able to refuel adequately, and part of Henry's training was food management. A swim of 12 miles in cold water burns up a massive 11,000 calories. Keeping it simple, eating the most natural foods available and making sure he gets protein in every meal, as well as vegetables and carbohydrates, are key. Making sure he stays well-hydrated by drinking water often is paramount, too. As the water temperature drops, he will also take in small amounts of warm water as he swims. The team has come up with a way of passing him a vessel with a small amount of water in it.
This is not the first extreme physical challenge Henry has taken on - he led the first relay swim around Ireland in 2006 and has completed lowest-to-highest-point expeditions on four continents. But this one is unique and is capturing the imagination of the public, as more and more people hear about his heroic attempt at the solo fin-swim.
With more and more people taking to the sea since lockdown, the sheer scale of what he is trying to do is appreciated by a larger number of people. As a seasoned sea swimmer, trying to get my head around a 12-mile swim is mind-boggling.
As the water gets colder, Henry plans to shorten his distance and quicken his pace. Right now, Irish coastal waters, while not warm, are only starting to dip. There have already been nights with ground frost and, as autumn turns to winter, the sea temperatures will plummet, making Henry's task even more arduous.
His army training, he knows, will serve him well. "When I'm getting cold out there or the waves start to toss the boat about, I can dig into those reserves. I can also tap into what I've done in the sea. I respect the sea. There's a saying, 'Ná tiontaigh do dhroim ar an fharraige choíche,' which means, 'Don't ever turn your back on the sea,'" says Henry, a native Irish speaker.
So much of the expedition has been made possible by people giving up their time and talent. Willie Duggan, owner and skipper of the Tor Dearg, Tory Island's fast ferry, is sponsoring the trip. Rory O'Donnell, a skilled and much-in-demand photographer, is giving his time free as well. Both the photographer's mother, Annette, and younger brother Colm are cancer survivors and he was keen to get involved when approached. Capturing Henry's progress means immersing himself in the water.
As the boat pulls out of the port of Greencastle to go to sea, the day brightens and the water sparkles. There is no sign of the storm to come and the sea rolls gently. We stand on the edge of the Tor Dearg and take a step off and overboard, momentarily sinking beneath the waves before popping up again into the sunlight.
This is Henry's element, a place he feels completely comfortable. He knows his capabilities and respects the ocean. As we swim, heads down, lifting our arms out of the waves to catch and pull ourselves forward, we fall into a leisurely rhythm. I can't help but think that not all days in the sea will be like this one and, with winter setting in, the task ahead for Henry is a giant one.
As we stop to look around, we bob up and down in the water. Henry makes a joke about the movie Open Water, in which two tourists are abandoned at sea by the boat that took them out on a scuba-diving trip. The sun breaking through the clouds warms our faces and I feel like I could stay here for hours and listen to Henry's ocean adventures. A small pod of dolphins swim past, keen to get to their destination. I am reminded that we are in their space now.
Back on board, Henry explains that, as well as raising money and awareness for the Irish Cancer Society and Water Safety Ireland, he wants to spread the message about being active through all the stages of your life.
He says he's known much younger men who pack in exercise at the age of 30 when their footballing days are over. But he says he wants to bring with him a message about engaging in activity that's consistent with your ability and not your age.
In 1992, Henry sustained multiple life- threatening injuries during the bike section of a triathlon. He broke his neck and spent a year in recovery. He believes that, no matter what your level of ability, you can still find an activity that will enhance your life and give you a better quality of life. "If you can improve your quality of life, you'll feel happier.
"You don't have to accept the norm in society that when you get to a certain age, you should stop doing stuff," he says.
He believes that while his challenge is a personal one, everyone should find something to challenge them. "We've lost the ability to tap into our innate capability to survive in conditions that present us with challenges. People never discover what their abilities are because they don't try things. Any physical activity is of huge benefit, and the benefits of swimming are well-known."
Docking back in port, I wave goodbye to Henry and his crew. That night, a storm rolls in, lashing the coast of Donegal with wind and rain. It's no weather for swimming, and Henry will get a chance for a well-earned rest before it's back to business.
His challenge is a momentous one that formed when he was just a boy. The sea called to him then, and it's calling to him now.
Henry's only response was to get in and swim with all his might.
For more information on Henry's progress or to donate, see idonate.ie/FinSwim2020