The comedian made a splash with Fiona Lambert, who has stage four cancer, after reading about her charity sea dips in the Sunday World Magazine last weekend.
Chatting exclusively to the
Sunday World the mum-of-three revealed that if she could take a dip with one celebrity it would be the RTÉ funnyman.
Touched by the 42-year-old's revelation, PJ was determined to row in beside Fiona, who was diagnosed with breast cancer in 2017.
Harrowingly, just two years later Fiona's cancer returned, and this time, it was incurable.
Speaking to the Sunday World, PJ said: "I was over in my mam's and I had bought the Sunday World. I was just sitting there when someone text me to check out page 14 of the mag. So I did. I'd had a really shitty week but I got a massive lift from reading Fiona's story and her mentioning that she would like me to go for a swim with her. She could have asked for George Clooney but she asked for me. What an honour."
Determined to track the Dubliner down, the star asked for social media's help in tracing the brave mum.
"This is Ireland. It's tiny. So it didn't take long to track her down on social media and arrange a swim on Monday.
Joining forces at Dollymount Beach, the duo launched themselve into the Irish Sea, braving freezing temperatures for charity.
"I honestly got more out of it than Fiona did. She's incredible. She was on day 26. I was only on day one.
"I hate sea swimming so much. I'm not at all into it. I volunteer for the lifeboats so I am in the water a lot but I am always in full wetsuits and life jackets.
"But it was Baltic on Monday evening when we went. Fiona said it was particularly cold that night to be fair. But she could have just been saying that to me to make me feel better.
"It was very easy and comfortable. She had a few mates there with her as well. We spent about five minutes in there and had a laugh afterwards. I genuinely found it to be hugely uplifting."
So is he hooked now? "I won't be seen dead in a Dry Robe if that's what you are asking? But I will definitely go in again."
For Fiona, who completed her 30-day swim challenge on Friday it was a dream come true to have PJ paddling by her side.
"He left me a voicemail last Sunday and he just said, 'Hi Fiona, it's PJ, I believe we are going for a swim.' You know his voice, it's just so distinctive, I couldn't believe it. I am definitely going to keep the voicemail."
It wasn't all laughs though as the beloved comedian had to be coaxed into the water.
"He is so genuine and down to earth, he did say 'I am just letting you know I am going to be a baby in the water.' It was funny getting because he said, 'I don't know how people think this is good for your mental health, it's cold and I am freezing, it's miserable.' It was all good fun and in the end he really enjoyed it."
Having raised a staggering €19,000 over the course of her fundraising drive, Fiona said PJ also dug dip for Breast Cancer Ireland and the day oncology ward in Beaumount Hospital
"He donated €500, I couldn't believe it, he is so generous.
Speaking of the huge reaction from her interview, she said: "I really didn't think anything would come from the article, I was a bit nervous about it coming out because it is a little surreal reading that stuff about yourself but I have gotten great feedback from the piece in the magazine. I really wanted a realistic, positive message to go out and for people to know that you can still live well with this diagnosis and that's what I got. My phone just blew up on Sunday.
"Last week was really difficult but PJ definitely gave me the boost and the morale to keep going. I can't believe how much money we have raised."
To donate check out ie.gofundme.com/f/30-days-of-sea-swims