It's Australia's ultimate endurance challenge: four days, two islands, three mountains and 335 nautical miles of water in between.

Each year at Easter, competitors from across Australia and overseas take part in the Hydro Three Peaks Race. They set out from Beauty Point on the Tamar River, north of Launceston.

Their challenge is to sail north to Flinders Island, scale Mount Strzelecki and then sail south along the east coast to Freycinet National Park for a clamber up Mount Freycinet's granite slopes. Then its on to Hobart and into the Derwent River, before a final run to the peak of Mount Wellington and back to the city.

Its four days of non-stop running and sailing: 133km and 335 nautical miles.

You can be there to cheer them on, or better still to take part. While the challenge is enormous the beauty of the landscape is unbeatable.