A fundraising father swam to France on Thursday but ‘impossible tides’ thwarted him from swimming all the way back again.
Michael Brennan, 32, from Streatham Hill, swam 30 miles in 18 hours while attempting to become the 25th person in 50 years to double cross the Channel.
Mr Brennan set off from Dover in the early hours of Thursday to raise money to support research into kidney disease, which affects his children Amelie, five, and Ciaran, three.
"Totally stoked with swim and all support. Thanks Crew!!" posted his Twitter account Kidney Splash.
Before embarking on the 22-mile swim to Cap Gris-Nez in France, Mr Brennan said his success depended on the weather.
He said: "I have been looking for something to do to raise money for research because my family suffer from kidney disease.
"As part of that I want to take the opportunity to raise awareness about organ donation."
Visit kidneysplash.com to donate.