That swimmer is Australia's Grant Hackett, the undisputed king of the 1,500 metres freestyle, the longest and most gruelling event on the Olympic swimming programme.

Hackett is unbeaten in the 30-lap race since 1996 and is so far ahead of his rivals that his reign seems certain to last for years to come.

He won the Olympic title in Sydney four years ago and has won the past three world championships. More often than not, he laps the entire field, and no-one has got within half a lap of him for years.

Hackett's world record of 14 minutes 34.56 seconds is more than seven seconds faster than anyone else has ever swum and more than 22 seconds clear of his nearest challenger for Athens.

Complacency looms as his biggest obstacle in Athens but the 24-year-old Hackett has lost none of his motivation.

At a training camp in July, he told reporters: "Each year...when it comes to that event, I feel more motivated than the year before. It definitely does excite me.

"It'd definitely be nice to hold the winning streak that I have, not only this year but for many years to come."

AMERICAN OFFER

Hackett's domination of the 1,500 is beginning to take on epic proportions with the United States offering $1 million to any American who can beat him and take his world record.

But Hackett has no intentions of letting his standards slip. Although long-distance swimming can be lonely, Hackett has never tired of churning through the laps.

He estimates he has chalked up 11,000 kilometres in training since the Sydney Olympics -- about two-thirds of the distance between Australia and Greece -- and is in far better shape than when he thrashed the field to win four years ago.

"My times in training as opposed to back then could not even compare. I'm so far ahead of anything I did in that preparation, it's not funny," he said.

"I do feel a lot more experienced, not only physically, but mentally more so than anything. I know what to expect. I'm a lot more relaxed."

Tall and skinny with a massive armspan, Hackett has the perfect build for a long-distance swimmer but his versatility allows him to swim every distance from 200m to 1,500m.

He once held the world record for 200m and is the second fastest swimmer in history over 400m, but has had the unfortunate timing to run into Thorpe, whose grip on the 200m and 400m is almost as tight as Hackett's on the 1,500m.

FAVOURITE RACE

Hackett's achievements have largely been overshadowed by Thorpe's success but there has never been any hint of animosity between them and the pair are the best of friends.

When Thorpe was reinstated in the 400m after his disqualification from the Australian trials, Hackett was the first to offer congratulations even though he would have been favourite to win gold in Athens.

While Thorpe is probably Australia's most popular swimmer, the 1,500m is the country's favourite race. It has captivated the country since Andrew "Boy" Charlton won the event at the 1924 Paris Olympics as a 16-year-old and each of its winners has become a national icon.

Murray Rose (1956), John Konrads (1960) and Robert Windle (1964) all won the race once each while Kieren Perkins won back-to-back titles in 1992 and 1996.

Hackett denied Perkins an historic treble when he beat him in Sydney but is already eyeing a third title in Beijing in 2008 if he wins in Athens.

"I love the pain tolerance. I love the mental challenge of having to push yourself to the absolute extremes," he said.