He was wearing a lifejacket and was not injured during the ordeal.
"He was just a bit cold and a bit tired, we got him on board and gave him an assessment.
"I think he had been in the water for about an hour," Coast Guard duty skipper Glenn McAdam said.
"He wanted to attempt to flip the catamaran, but after a few goes, we towed the boat as close to shore as possible, then [the catamaran skipper] swam in with one of our crew to assist him."
Mr McAdam was not sure exactly how the boat had flipped but noted the conditions were "quite rough", after the wind had picked up.
"I'm not sure how experienced he was, but he had a lifejacket on and was doing everything right as far as I could see."
The stranding was a reminder to always wear a lifejacket, carry two forms of communication and notify someone of your whereabouts.