James Seaton stripped bare and climbed into the chilly water after Lhasa Apso puppy Milly jumped in and got into difficulties.
His mother, Margaret Gillespie, explained her son was walking the dog near to the Robert Burns Film Theatre earlier this week when it escaped him.
She said: “He had her off the lead and she was just running about and then she was in the water.
“We don’t know what happened, maybe she thought it was just another bit to walk.
“She ended up in quite a deep bit, the water was fairly shallow all round but she was in a bit of a hole.
“The water was moving fast and he said she was getting swept away so he took off his clothes and went in to the water to get her.”
Mr Seaton, 48, is quite confident in the water, his mother explained, as he used to be in the Royal Navy.
But she commented that the water was decidedly colder than he is used to in Ibiza, where he now lives and owns a bar.
Margaret said: “When he came home he had the dog wrapped in his sweatshirt and they were absolutely freezing.
“Milly had a wee coat on so it’s a wonder she never got dragged under with the weight of it – she’s just little, only about 18 inches.
“She started to get into trouble and he thought ‘if I don’t go in for her she’ll end up at Glencaple’.”
Praising her son, Margaret said: “I am so delighted, but he doesn’t think he’s done anything special.”