Stars in the event, which begins on Wednesday, include Olympic gold medallists Emma Snowsill and Kenny Wallace, triathlete Courtney Atkinson, seven-time surf champ Layne Beachley and Mad Max stuntman and former ironman Guy Andrews.

Adventure race specialists Jarad Kohler and James Pretto won last year's five-day event but believe the strong field, unpredictable West Coast weather and a tense rivalry between top competitors could create a classic this year.

``I think this year's event is going to be super-close,'' said Pretto, whose parents will also be competing.

``The competition is as tough as any races I've competed in and this year is going to be even tougher.''

The professional sports stars, however, could find it tough to be in contention as the unique combination of kayaking, mountain biking and trekking over five long days is a challenge for even the world's best athletes.

``I know how to ride a bike and run, but it's a different skill when you have to go off-road - it's completely out of my comfort zone!'' Snowsill, who won gold in the Olympic triathlon in 2008, said.

``Our racing schedule means I haven't had many opportunities, but when I did get out and tried this sort of `off-road adventure' it somehow scares me but excites me at the same time.

``I am used to having to go flat out for a session, rest, recover and go again, but I am the least fit I have been in my whole life so I am surrounding myself with some much more experienced people in this type of environment.''

Having raced in the event last year, experience tells Atkinson the first step is finding his way.

``It's better to be going slower in the right direction than quicker in the completely wrong one,'' he said.

``This and the Olympics are obviously two completely different experiences.

``The Olympics is the pinnacle of sport. But this is a tough but enjoyable and rewarding challenge in some of the most amazing locations you can imagine.''

While the Olympians may make an occasional appearance at the front, the main contest is expected to be between Australians Kohler and Pretto, of Swisse Active, and New Zealand racers Richard Ussher and Braden Currie.

Ussher finished second with Currie for Team Tasmania last year but was struck down by illness and is confident the pair can fight harder for victory this time.

``They (Team Swisse) raced well but we'd like to think we have the measure of them this year,'' Ussher said. ``We'll certainly be giving it full gas every day.''

Tasmanian Mark Hinder, who won in 2011, is also hoping to challenge for top honours.

``I'm excited to be able to take on the world's best adventure racers in my home state  and I'll also try and dish out some pain to the Olympians in a race that is a bit outside their comfort zone!'' Hinder said.

``The scenery each day is outstanding. This year we'll complete the loop around all the major national parks in Tasmania, so I am looking forward to some new racing locations.''

Webber, who was one of 10 racers in the first cross-Tasmania event back in 2003, will be absent for the first time due to team commitments.

Instead, he will send his prot?aacég?aacé, Mitch Evans, who is climbing the ladder to F1 and spent this season in GP2. ``He's given me a bit of advice,'' Evans said. ``He thinks I will be fine, as we train together most of the time he has a good idea of where I'm at.

``I have high expectations in terms of it being seriously tough mentally and physically. I can't wait to test myself.''

Webber, who competes in his last F1 race this weekend in Brazil, will keep a close eye on events unfolding in Tasmania.

He hopes his departure from F1 will allow him to develop and compete in more events like the challenge, and he has already earned the respect of many racers in the adventure racing community.

``Mark's got a huge amount of talent in sport away from the car,'' Ussher said.

``I've no doubt if he'd chosen a different path to pursue when he was younger endurance sport was probably something he could have done very well at.''