Open water swimming's poster girl Keri-Anne Payne made history when she took silver in the very first Olympic 10K marathon swim in Beijing. A year later she followed this feat with gold at the 2009 World Championships.A true water baby, Keri

Mark Kleanthous is a founder member of the British Triathlon Association and member of the Great Britain triathlon team. Over the past 30 years, Mark has completed 71 marathons in under three hours and finished more than 420 triathlons, including 31

triathlons [a national series for youngsters] and after that I was hooked."The appeal is simple: "It's the new challenge. Marathon was the big challenge for a while, and now it's triathlon. Most people are good at one of the disciplines so it encourages them

. My main advice is that it's not super hard. Choose the right distance for you and you'll be able to do it. It's not like running a marathon where you're pounding on your legs for hours and its high impact. Triathlon is really fun; find a friend