Sharks, stingers and sunburn are not the only dangers swimmers have to contend with during the HBF Rottnest Channel Swim - one of the biggest medical risks is hypothermia.
Sorrento swimmer and former triathlete Paul Laver, 28, knows the danger of hypothermia, which occurs when the body's temperature plunges below normal, all too well.
After taking the leading solo position for most of the way in the Rottnest swim last year, he was hauled from the water, confused and vomiting, just kilometres from the end.
It was his first solo attempt after being part of a winning duo in 2010. His memories of the event are sketchy.
"I was just very disoriented," he said. "I had no spatial awareness and I couldn't swim in a straight line. I could barely even keep my eyes open."
Mr Laver, who works in the disability services industry, said he "started losing the plot" about 12km into the 19.7km event.
He was pulled out of the water about the 16km mark, after swimming for more than 3½ hours.
One reason he succumbed to hypothermia was he could not stop vomiting, caused by fumes from his support craft, which had been positioned to shield him from the wind.
He has overcome his disappointment and will seek to put his stamp on the event again next month by competing as part of a four-man team.
Mr Laver said the one sure way to prevent hypothermia was to add some body weight.
Swimmers will take to the ocean off Cottesloe beach on February 23.