From the organiser's website (Human Race):

We're excited to be staging our first ever open water swim event at Dorney Lake on 11 July and are thrilled to announce that Maarten Van Der Weijden, who won gold in the 10km marathon open water swim in Beijing, will be taking part as an ambassador for title sponsor, blueseventy. Over 1000 participants are expected and Maarten will be there to swim alongside and also as an encouragement for novice swimmers.

Competitors can choose from 1km, 1 mile and 3km race options, giving swimmers of all levels of ability the chance to take part - and a perfect opportunity for those in Ironman training. All swimmers will receive a special blueseventy event t-shirt and the first Male and Female in each distance will also win a brand new blueseventy Helix wetsuit (voted wetsuit of the year 2008) worth £350. Entry into the 'blueseventy GreatBig OpenWater Swim' costs only £20 at www.humanrace.co.uk

For more details follow this link.