Paddy Conaghan, 80, says people think he's crazy, but it was the only physical feat he could think of to raise money for charity.

"I can't climb mountains anymore", he told Sky News on the pier at Roundstone, County Galway. "I can't run anymore, I can't cycle anymore, like I used to do. But I can do a bit of swimming and diving."

Paddy, from Arranmore island off the coast of County Donegal, began his journey in early December in his home county, in the northwest of Ireland, and thinks it will take him two months to complete.

Paddy admits he's a "novice swimmer", who only learnt to swim again "in the summer when the weather was getting good. A novice, more or less, after 60 years."

Now, he's driving south along the Atlantic coast in his small van, trying to cram quick swims in at as many stops as possible each day.

Breakfast is typically steak and eggs in the back of his van. At night, he says he usually has two pints of Guinness at a local hostelry, before retiring to his improvised bed in the van.

Pointing to a mattress, he says: "See that bed there? It's the best I ever had. You could go into a hotel tomorrow and pay £250 for a bed and I wouldn't be able to sleep in it. That bed, there, just knocks you out."

It seems like a physically challenging environment for a pensioner, but Paddy says that a tough working career in the UK helped to prepare him.

"I started off in a coal mine in Scotland when I was 16, then I moved to Wales, worked in coal mines there," he says.

"I worked in tunnelling, then moved to London and worked on tunnelling on the Victoria Line [in the 1960s]."

"I lived in a van, on and off. I'd sleep in cabins and caravans, just following the work."

The goal of his epic journey is to raise money for Gemma's Legacy of Hope, a Donegal counselling service, and tens of thousands of euros have already been raised through a GoFundMe page.

The 80-year-old trained in ice baths for 10 months.

So why not do it in the summer instead?

Paddy, laughing, says: "Somebody would say 'see that guy there having a great time around Ireland, swimming in the summertime, enjoying himself'!"

"It's a challenge," he adds. "You're not going to get any money if you're enjoying yourself, are you?"

He says he's "enjoying" the dips so far, despite the frosty conditions. "The water's not cold yet, I know it's going to be cold…it's going to be a lot colder."

Paddy will be on the road, and in the water, throughout the festive period, which includes his 81st birthday on 8 January. His adult children are following his adventure online.

Do they think he's mad? "Yeah, something like that," he says. "They say 'what's wrong with this guy?'"

Donations to Gemma's Legacy of Hope can be made at Paddy Conaghan's fundraising page here.