The swim around Hong Kong Island clocked almost 11 hours.
But the gruelling challenge made a big wave, with swimmer Alex Fong generating HK$7.9 million (S$1.37 million) for A Drop Of Life charity that aims to help people in Cambodia, China and Nepal gain access to clean water.
On Tuesday (Nov 5), Fong, 39, who swam for Hong Kong at the Sydney Olympics in 2000, took the plunge at 5am to tackle the 45km swim.
The actor-singer told media that he had to overcome cramps and huge waves but soldiered on, buoyed by the thought that his effort would help needy folk.
"Today is the most successful day of my life," he said.
Jeannie Chan, 30, who is rumoured to be his girlfriend, was at Sandy Bay when he finished the swim, reported the HK01 portal.
She had texted Fong that she could not be there at 5am because she was "filming dramas" and could wrap up work only at 6am.
"But I didn't think she'd be able to come before work resumed, to see me complete the swim," said Fong, who logged more than 400 hours of training to achieve his goal.