Open-ocean swimmer Adam Walker: 'Hardest swim of my life'

Adam Walker hopes to become the first Briton to complete the Ocean's 7 Challenge

During the swim, Mr Walker said he saw a six foot shark pass underneath him

Jellyfish stings, being flipped over by waves and encounters with sharks - just some of the hazards faced by an open-ocean swimmer during his latest challenge in Japan.

Adam Walker, 34, from Huthwaite, Nottinghamshire, swam 18 miles (30km) across the Tsugaru Channel, last month.

It was the fifth stage of the Ocean's 7 Challenge - a series of long-distance swims scattered across the globe.

He described it as "the hardest thing I've ever done in my life".

Mr Walker is aiming to become the first Briton to complete all seven swims, at the same time raising money for marine charities.

'Terrible pain'

During his latest challenge, which started on the 14 August and lasted more than 15 hours, he was stung by several jellyfish and "smacked in the face" by large waves, which he said made him "instantly sick".

Mr Walker said he also saw a 6ft shark swim underneath him.

The swimmer said at one point the large waves and strong currents had taken everything out of him.

"I've never breathed so hard in my life," he said.

"My chest was tight and my shoulders were really sore from the hours of swimming and being bashed around."

He added: "At one point my left shoulder had packed in and I had a terrible pain in the middle of my right shoulder, but was determined to finish."

The 34-year-old said he had been spurred on to the finish by the sight of a lighthouse on the coastline.

"With 800 metres to go, I started sprinting like my life depended on it," he said.

Mr Walker has now completed five of the seven swims, which include the English Channel, Straits of Gibraltar, Molokai Channel in Hawaii, the Catalina Channel in the US and the Tsugaru Channel, Japan.

He has now started training to swim the Irish Channel and the Cook Strait in New Zealand, which he hopes to do next year.

The feat has only ever been completed by one person - Irishman Stephen Redmond - but not all seven swims were successful on the first attempt.

Adam Walker is aiming to become the first Briton to complete all seven swims, at the same time raising money for marine charities.