SYDNEY, Australia (AP) – Ian Thorpe realized he could do only so many strokes, so many laps. It was time to discover life outside the pool.

Tired of endless training and looking for something better in life, the five-time Olympic champion retired at 24 Tuesday, ending a career in which he ruled his sport like few others.

“You can swim lap after lap, staring at a black line, and all of a sudden you look up and see what’s around,” Thorpe said at news conference. “That’s what it feels like to me.”

Thorpe won the 200- and 400-meter freestyle events at the Athens Olympics, which turned out to be his last major international meet.

Then came a yearlong break to overcome “mental fatigue,” a bout of glandular fever that kept from the Commonwealth Games and minor injuries that affected his training. All of which meant the “Thorpedo” and his size 17 feet have been missing from the world’s pool decks for more than two years.

Teammate Grant Hackett called it a sad day for the sport.

“Not just for Australian swimming but for world swimming,” he said. “They’ve lost one of their great athletes and a guy who has brought so much to the sport.”

Thorpe won 11 world titles and set 13 long-course world records.

“It’s been a tough decision to make,” Thorpe said. “I had to pick a time, that was the time. None of my goals included breaking any more world records. I knew how to do it, but it wasn’t as inspiring as it should have been.”

Thorpe said there was nothing significant about the hour he chose to retire. But after years of checking the clock after each race, he could not resist the impulse to note the precise time of such a crucial decision.

“I needed a closing point,” he said. “So I looked at my watch and that was the time. It’s as simple as that.”

Thorpe burst onto the swimming scene as a teenager and broke his individual long-course records between 1999 and 2002, becoming an international star after dominating the Sydney Olympics. He won three gold medals at the 2000 Games – all world records – and two silver medals.

“I’ve reached all the dizzying heights of this sport,” he said. “I’ve had a tremendous amount of success. I’ve also had setbacks – the last round of them sent me to L.A.”

Thorpe went to train in California this year to escape the scrutiny at home. Still, critical reports surfaced in local newspapers questioning his conditioning and dedication. But Thorpe said he was as physically fit as he has been in a long time, and he started to get “mentally fit.”

He said he hoped to be remembered for the manner of his retirement, his decision to quit on his own terms. He is not sure what’s ahead.

“It’s a very dark question for me. Swimming has been a security blanket,” he said. But “I haven’t balanced out my life. I realized I had to prioritize other things and had to let swimming take a back seat. I’m looking at the next phase.”

American swim star Michael Phelps called him an “inspiration and a terrific champion.”

“He elevated the worldwide interest in swimming and was a great ambassador to our sport,” Phelps said in a statement.

Asked if he would stage a comeback for the 2008 Beijing Olympics, Thorpe replied: “I never rule anything out, but it’s not going to happen.”

Thorpe considered his best Olympic performance his last one – winning gold in the 400 at Athens “because of the state I was in before I swum it. I was really struggling and I was able to lift myself to get there.”

And his proudest moment? His retirement speech.

“Everyone will remember what I did in the pool,” he said. “But this is one of my proudest moments in being able to stand up here and do this today.”

AP-ES-11-21-06 1639EST