Not content with a normal marathon across 42km, the ultrarunners yearn for something bigger and more testing.
When we think of endurance sports, we might think of Ultramarathons or Ironman triathlons.
But there’s a new discipline in Sweden that’s gaining a reputation as one of the toughest in the world.
It’s called swimrun. Team of two swim and run a total of 75km among and over 26 islands in Stockholm’s archipelago.
It’s now in its 10th year and gaining popularity.
Paul Rhys explains.