One of the country's most extreme races will return to Scotland today after five years.

Around 100 participants in the Glen Nevis River Race will brave the icy waters of a two-mile stretch of the River Nevis - on Lilos. They will begin by launching themselves off a tiny ledge on a high rick at the head of the glen.

They will then have to follow the deepest course of the river through rocks and rapids, negotiating major obstacles such as the Gurgling Gorge, Dead Dog Pool, the Leg Breaker and a 30ft waterfall, the Lower Falls Leap, before finishing in the calmer waters further down the glen.

Flippers and other swimming aids are banned for the event, which is designed to raise money for the Lochaber Mountain Rescue Team, but competitors must have an inflatable craft with no sides. Many are expected to turn up in fancy dress on top of their wetsuits.

The Glen Nevis River Race is a timed event and the time taken to complete the hazardous course is dependant on the water levels at the time. As a result, times have varied from around 20 minutes to in excess of an hour. The state of the water also determines the amount of minor scrapes and bruises.

The race stopped in 2003. In its previous 30-year run, it enjoyed a high profile as a fund-raising spectacle. Former Blue Peter presenter John Noakes, musician and TV presenter Dougie Vipond and Blythe Duff, star of TV's Taggart, have tried it.

More than 3000 people have taken part in the event, raising thousands of pounds for the rescue team.