Perhaps one of the toughest sports in the games, triathlon is a combination of swimming, running and cycling.
Competitors have to swim in the sea for 1,500m, ride bikes on roads for 40km and then run 10km on roads too.
And it's not as if they get to ride and run on flat bits of land either, the cycling bit of the course has a big hill in it, but that's not enough of a challenge for some.
A US triathlete, Barb Lindquist, says the cycling course is too easy!
Who are the British hopes?
Andrew Johns is a former European champion while Tim Don was the world junior champion back in 1998.
In the women's event all three competitors are solid, but face a huge battle to beat some very strong competitors from other nations.
Who are the big names?
Australia is so confident in the women's event it felt able to leave the 2003 world champion Emma Snowsill out of its trio for Athens.
In her place goes 19-year-old Maxine Seear, who was picked ahead of Aussie legend Michellie Jones too.
But it's Lindquist who is the world number one, and she's been in the world's top five triathletes since 1999.
Australia is also strong in the men's event, with Greg Bennett hoping for gold after being the world number one for almost two years.
Spanish star Ivan Rana, who is awesome on the running section, could upset the normal order which sees Australians, Americans and Canadians dominate the event.