Swimming legend Ian Thorpe has completed the first official training session of his comeback in front of a huge media contingent at the pool that bears his name in Sydney.

The five-time Olympic champion completed a range of training exercises in a private lane at the Ian Thorpe Aquatic Centre.

Hitting the water at 6.30am, Thorpe completed a two-hour session under the watchful eyes of Swimming Australia head coach Leigh Nugent and performance science manager Bernard Savage.

Swapping the iconic long black swimsuit for a pair of briefs - following rule changes on race swimwear during his four-year absence - Thorpe's every stroke was captured by at least a dozen cameras.

Thorpe, who began training last September, described the session as an "average" hit-out.

"I didn't feel that much different than I did yesterday except I knew I'd have everyone here watching this morning so I had to make sure I was working my turns a little bit better this morning and keeping myself on my toes," said Thorpe.

"But I feel good about it.

"...It's felt much worse. This was an average session for me so I was happy with that.

"I'll probably get on with it and be absolutely over it and buggered by the end of the week."

Good friend Geoff Huegill was also on hand as Australia's highest-profile sporting comeback publicly swung into action.

"It is quite a good sight, he moved quite effortlessly up and down the pool," Huegill said.

"It's going to be quite exciting."

Nugent said swimming's governing body FINA had confirmed Thorpe can begin swimming competitively on November 2 after he registered with international drug-testing authorities.

David Beniuk
AAP