Simon Mardon is the defending champion of the Abel Tasman Coastal Classic but today he faces stiff competition from outstanding United States Army athlete Matt Cavanaugh.

The 31-year-old American is a captain and strategist for the US Army and is excited to make his debut in the event on his first visit to New Zealand.

He and his wife Rachel are in New Zealand for the next two years, while Cavanaugh completes his Master's in Strategic Studies at Victoria University's School of Government.

Cavanaugh brings an impressive running record as the Top US Army finisher at All Armed Forces and National Cross Country Championships and the US Army Athlete of the Year in 2009.

He met top New Zealand mountain runner Anna Frost at the Trans Rockies Run (117-mile stage race in the Colorado Rockies) in the US, where he placed fourth, and she highly recommended the event.

"It's not so much what I've heard as what I've seen via photos people have posted about the event ... it is breathtaking," said the 31-year-old Cavanaugh.

"I'm not sure I'll be able to keep pushing out a hard pace if it's as gorgeous as I think it'll be - I'll have to pause and enjoy it once in awhile."

Cavanaugh is the real deal and has a great record of running success.

But he is more proud of his fundraising and awareness work with the Wounded Warrior Project - a not-for-profit organisation dedicated to honouring and empowering the most severely wounded veterans from Iraq and Afghanistan.

"I've been their grassroots fundraiser for the past two years and I'm proud we've raised roughly US$95,500."

Simon Mardon, the winner in 2007 and 2009, said you never knew who was going to turn up for the event which boasts spectacular views and he was up for the challenge.

"It is the most enjoyable run that I have ever done," said Mardon, a 37-year-old school teacher.

"It is really unique in the way you get boated in on to a beach and the only way home is 36km of up and down though the national park."

Mardon does not feel any pressure as the defending champion but just enjoys running the Abel Tasman National Park track.

"There is only pressure from myself," said Mardon.

"I will be giving it my all and holding nothing back - hopefully that is enough."

Established in 1994, the Abel Tasman Coastal Classic 36km Offroad Run has become one of the most popular off-road runs in the country.

Chris Gates, alongside Colin Rolfe and Owen Rowse, has competed in every event since its inception.

"You have to get your priorities right and it is always the first thing in my diary," said the 51-year-old.

"It's a good, honest run and there is nothing like it - I am not surprised how popular it has become."

It sells out every year and entrants know when their boat journey ends and they are dropped off on the golden sandy beach of Awaroa they have a long way to go to Marahau.

Entries are restricted to 300 athletes as the Abel Tasman Coastal track is owned and maintained by the Department of Conservation.

"It is the premier coastal track in New Zealand and is really achievable for most runners," said Graeme West from Nelson Events.

"It is a well organised event, the national park is really special and they get to run it in a day and they get really well looked after so they can just focus on the run."

West explained that the 36km run is the equivalent to a full marathon on the undulating off-road terrain.

"All of our events have three ingredients: mystery, history and scenery and this one is special in that it has all three.

"The mystery in the Abel Tasman Coastal Classic for many is when the Marahau finish line is going to appear."