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Jacob Burenius emerged from the water after one of 24 stretches of open water swimming in the Otillo race last September in the Stockholm archipelago.

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Competitors in the Otillo race crossing the island of Sandhamn in Sweden. The race, which began as a bet among friends, involves swimming a total of 6.2 miles between 26 islands and running 40.4 miles across them.

NYT: The 46.6-mile Otillo race started as a drunken bet among four friends in 2002. The challenge? Race in pairs from Uto to Sandhamn, two islands in Sweden’s archipelago, which required swimming a total of 6.2 miles between 26 islands and running 40.4 miles across them. The last team to finish had to pick up the winners’ hotel, bar and dinner tabs on the final island.

Today, the Otillo features 240 competitors, with an additional 1,100 who want to race but can’t because of size limits. It is one of the world’s toughest endurance events and an example of the burgeoning popularity of off-road endurance competitions across the globe.

Off-road competitions pluck traditional endurance events, such as triathlons, running races and aquathlons, from their standard settings — cities, pavement and reservoirs — and place them in natural backdrops.

http://www.nytimes.com/2014/07/26/sports/taking-triathlons-into-the-wild.html?ref=sports