Dave Mullins claims he is an "unusually slow" swimmer, but with lungs burning and legs aching he smashed the world record for an underwater swim without a breath not once, but twice.
Yesterday, the Wellington man swam 244 metres underwater on one breath, blitzing a record he set on Friday by 18 metres.
Using a mono fin, Mullins swam nonstop for four minutes and two seconds, completing nearly five lengths of the 50-metre Naenae pool.
"You have to get it pretty much spot on," he said. "You're after maximum efficiency, so the turns are pretty important."
Mullins said that though he was an "unusually slow" swimmer, the sport was all about lasting the distance.
American judge Grant Graves said yesterday's effort at the freediving competition - hosted for the first time in New Zealand - was one of the biggest increases in a world record he had heard of. "It was a very impressive swim."
Mullins said it would take a few days to recover from the rigours of busting world records because of the buildup of lactic acid in his legs.
The weekend exploits would set him up nicely for the Freediving World Championship in Egypt in six weeks, he said. There he will compete in an ocean freediving event, in which divers go as deep as they can without breathing equipment.
Mullins practises holding his breath as part of his training, making his muscles work while oxygen-starved. Earlier this year he set a national freediving record, becoming just the fifth man to reach 100 metres.