CATS chief executive Brian Cook will continue one of his favourite traditions on Saturday by taking part in Western Australia's Rottnest Channel Swim for the ninth time.

The swim starts at Perth's picturesque Cottesloe Beach and finishes 19.7km away at Rottnest Island.

A number of people will complete the swim as part of a team, but Cook and 324 others are tackling the event solo.

"I have a personal goal of completing 10 solos," Cook told The Australian. "It’s a great personal, mental and physical challenge for me as I’m not a natural swimmer.

"[But] swimming has become an integral part of my lifestyle. Most mornings, right throughout the year, including winter, I jump into the seas off Torquay and Anglesea."

Competitors in the Rottnest Channel Swim raise money for the Royal Flying Doctor Service, Fremantle Volunteer Sea Rescue Group, Leeuwin Ocean Adventure Foundation and Starlight Children’s Foundation.

Cook, 60, sees the event as a worthy cause and a great challenge.

"I love the swim, the island, the feeling of accomplishment immediately after the race and standing on the foreshore," he said.

"The last 200m or so in the 20km swim is the best feeling."