People competing in the 75km Otillo Swimrun race in Sweden on Monday. To get to the end point, teams had to cross 24 islands, running and swimming to get there. The race started at Sandhamn, a small settlement in the Stockholm archipelago, and ended at Uto, a small island in the eastern part of the archipelago. A total of 320 athletes from 25 nations competed in this year's Swimrun competition that was born from a bet. It is a team sport based on two people who are linked by a leash several metres long and have to compete by running and swimming together. The race runs from dawn to dusk in and out of the water. There is 10km of open-water swimming and 65km of trail-running.