Athletes put their endurance to the test during Monday's Otillo Swimrun race that started at Sandhamn, a small settlement in the central-peripheral part of the Stockholm archipelago, and ended at Uto, a small island in the east of the Stockholm archipelago, a total distance of almost 75km.

The Swimrun competition, which was born from a drunken bet between two pairs of Swedes, is a sport that requires two teammates.

The team members are linked with a 10m leash, and have to compete by running and swimming together. Unlike a traditional aquathlon, which is a two-stage race combining running and swimming, Swimrun competitors tackle multiple legs of both disciplines.

Competitors have to complete the Swimrun course in the same equipment that they start with, which means they run in the same wetsuits that they swim in, and any items such as food or emergency gear have to be carried throughout.