Lewis Pugh is not a man for half measures.

The endurance swimmer and UN Patron of the Oceans became the first person to swim the length of the Channel in 2018, charting 328 miles over 49 days.

In 2007, he became the first person to swim across the North Pole and in 2010 he swam across a glacial lake beneath the summit of Mount Everest.

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In September Mr Pugh, 49, will be in Perth to give his talk, Achieving Your Impossible, and to receive the Royal Scottish Geographical Society's Mungo Park medal for his work in ocean conservation.

It will be his second visit to Scotland this year, after meeting Nicola Sturgeon in February to discuss the protection of Scottish waters at the International Marine Festival.

His deep love and respect for oceans was fostered in his birthplace, Plymouth, home to some of the world's most renowned explorers including Sir Francis Drake and artic expeditionist Robert Falcon Scott. His parents were both in the Navy and he joined himself before training as a maritime lawyer.

He said: "I think it's a combination of nature and nurture. The oceans have been very much in everything I've done."

Next year, Mr Pugh, who lives between South Africa and the UK, will take on his greatest challenge yet, a series of dangerous swims across the Commonwealth that will draw attention to his aim of having 30% of the world's oceans protected by 2030.

Mr Pugh has been instrumental in protecting over 2 million km2 of vulnerable oceans to date, but with only 7% of the seas secured, what would it take to reach his goal?

He said: "A complete mind shift. Our oceans are under threat from three things, overfishing, plastic pollution and climate change. And those three things come together to create this perfect storm."

The UK is leagues ahead of other nations, he said, yet there's so much more to be done.

"The UK is only one of 196 members of the United Nations. Not all 196 nations have coastlines but of those, there are some countries which haven't fully protected even 1% of that coastline.

"There are big nations like India, Japan and China who have a big impact on the world and we're encouraging them to truly understand the seriousness of the situation," he said.

"Everything that we do now, we must be looking at it through the lens of a climate emergency. Is our response to this kind of emergency adequate? And inevitably, it isn't."

There are 31 marine protected areas in Scotland with a further four, including an expanse at the tip of Lewis and the Southern Trench that stretches along the Aberdeenshire coast, currently under consideration for protected status.

Oil and gas drilling, industrial fishing, Navy gunnery exercises and seabed dredging all threaten the seas around Scotland.

Meeting the First Minister was eye-opening for Mr Pugh, when she shared with him the topic young people most commonly write to her about.

He said: "Over half of the letters she receives from children are urging her to take action on protecting the oceans and stopping plastic pollution. This is the next generation and that gives me great hope. It's the youth who are passionate about the issue.

"We rely entirely on oceans for survival. So we just can't be overwhelmed, we have to understand the role of the oceans, it's easy to turn your back because you can't see what's happening there. Unless you're like me, and you're in the ocean all the time. The fight is very, very clear and that is that the oceans are under threat."

Mr Pugh has witnessed first hand the devastating effect of climate change on the seas; rising temperatures, like the increase from 3 to 10 degrees he recorded in the seas around the northern Norwegian archipelago Svalbard, and rapidly shrinking numbers of fish and wildlife.

He said:"You don't have to be a scientist to realize if you got 10 degree water up against ice, it's going to melt. And that will have a profound impact on every person on this planet."

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During his channel swim he pushed himself through 10km daily and on most, had to endure swarms of jellyfish stinging him for around 3km.

He said: "Jellyfish never sting you on the toe, it's always on your face or your stomach - everything that's going through the water."

Mr Pugh's mental and physical fortitude is apparent but even he is worried for the future.

He said: "It scares me because world leaders, political and business leaders, are not seeing it or not responding quickly enough. We are winning some of the battles but overall, we're losing and we're losing very quickly."

His rigorous training requires him to swim in oceans almost daily so he can prepare for every condition. He has been hardened by his regular night swims in South Africa with the threat of deadly predators at every stroke.

He said: "Courage is a muscle, if you don't exercise it regularly, it softens up very quickly.

"On my swims in Cape Town everything looks like a great white shark. Every shadow looks like a great white shark, every piece of seaweed feels like a great white shark.

"If I didn't swim there on a fairly regular basis at night, when it comes to swimming in the Arctic, where you got polar bears, or swimming down in Antarctica where you got leopard seals and extreme cold, I would never be able to get in."

So, how does Mr Pugh achieve his impossible?

He said: "It's having a very clear vision. It's choosing the right team, it's meticulous preparation, it's never quitting. And then it's about having the flexibility to change when circumstances dictate. Life is long and short - if you're not doing what you enjoy, it's very long. If you're doing what you really enjoy it's short and quick - so you better make it count.

"I've seen the oceans change - not in a good way - and I'm absolutely determined to help governments create these large protected areas."