THE world's toughest open-water adventure race is to return to the Forth and Clyde Canal next spring, organisers have confirmed.

More than 300 swimmers took on the Red Bull Neptune Steps event in Glasgow in March this year.

Entrants travelled from as far afield as Canada, Switzerland and Lebanon to swim through 420 metres of cold water and climb 18 metres over eight canal lock gates in the world's only uphill swimming race.

Next year the number of competitors is expected to double to around 600.

Scottish champion swimmer Mark Deans, who has won five previous Red Bull Neptune Steps events in Scotland and Sweden, will be amongst the entrants as he defends his title.

The 22-year-old also set a new record for swimming 28.5 miles around Manhattan as part of the 20 Bridges marathon event in July.

He covered the distance in just six and a half hours.

On the Glasgow challenge, the endurance swimmer said: "I’m aiming to continue my unbeaten record, and keep on winning this event for as long as I possibly can. Each year the competition gets tougher and tougher, but I’m up for the challenge. In this sport, there’s no other event quite like it."

Entries open at 10am on October 24 at redbull.co.uk/neptunesteps.