Pippa Middleton celebrated her 32nd birthday by competing in the annual Otillo Swimrun World Championships in Sweden.

Script: It's the annual Otillo Swimrun World Championships.

A gruelling 85 kilometre race across 26 Swedish archipelago islands on foot and by the Baltic sea.

This year, Pippa Middleton took her place amongst the competitors along with her brother James and two other teammates.

SOUNDBITE Pippa Middleton, Duchess of Cambridge's sister

"It feels really special. It's been a tough race, a really tough race. It feels amazing to be here. Especially throughout the race. We had doubts about carrying on and how we were going to finish but we made it."

The Duchess of Cambridge's sister celebrated her 32nd birthday just the day before.

They completed the contest in 13 hours 4 minutes and 24 seconds.

Despite the exhausting experience, Pippa was still smiling after crossing the finish line.

SOUNDBITE Pippa Middleton, Duchess of Cambridge's sister

"The swims were really tough - the waves. I just remember moments in the middle of the sea just looking around trying to find my partner. It's been wonderful but one of the hardest experiences I've had."