"I resolved to follow my dream. I wanted to push every boundary. I wanted to swim further than anyone else. I wanted to cross seas and round capes that no one had dreamed of swimming before. And I wanted to swim in waters that were so cold no one thought it was possible to survive in them. And though it promised to make me poor and would take away the security provided by a career in law, that didn’t worry me."

"I could not believe what I was seeing: everywhere there were whale bones. Thousands of them stacked on top of each other. They rose from the seabed almost to the surface of the water. There were big bones. I could make out many of them: rib bones, jaw bones, vertebrae. In some places they were piled so high that, when I took a stroke, my hands touched them. I thought of all the beautiful whales I’d seen around the coast of South Africa and Norway that add so much to the area. How many whales were hunted and brought to this island before having their carcasses burned for oil and their bones dumped in this way? It disgusted me to such an extent that I considered stopping the swim to move it elsewhere, but I decided I had to press on."

"I have been haunted by that swim through the whale graveyard and haven’t been able to get the image of the bones out of my head. Man hunted whales almost to the point of extinction, not seeming to care that we would lose one of the wonders of the sea world forever. It is the coldness of the water in Antarctica that preserves the bones and makes it look like they were left there yesterday but I like to think they are there as a reminder of man’s potential for folly."

"...when you swim from England to France you’ve got to leave your doubt on the beach at Dover."

"When people say to me, you must have a very strong mind to swim across the North Pole, or off Antarctica or on Mount Everest, I tell them that endurance swimming builds good mental strength."

"I don’t know of any sport where the goalposts can shift the way they do with endurance swimming."

"Thoughts alone won’t make extraordinary things happen. But nothing ever happens if you don’t visualise it first."

"A massive turquoise glacier feeds into Magdalenefjord, with chunks of ice as big as buildings breaking off and landing in the water to float away as icebergs. As I swam past them, with my head in the water, I heard a tantalising sound: a snap-crackle-pop, just like Rice Krispies in milk. It was the sound of tiny air bubbles being released from the ice – air that had been trapped there as much as 3,000 years ago. To swim through this sound, I thought, is to swim in history."

"They have [...] a split personality. One moment they’re your best mate, and next they are trying to drag you down to the bottom of the sea to drown you. [...] It’s just astonishing."

"The essence of any great achievement is to believe in your purpose."

"I knew now that I had to stand up and start speaking about protecting our environment. From that moment on, every swim should have the aim of inspiring people to protect and preserve the world’s oceans and all that live in them."

"The most powerful form of self-belief comes from believing in something greater than you. Because when you’ve got purpose, everything becomes possible."

"I’m not a rule-breaker by nature. But there are times when you need to untangle yourself from red tape. Because the truth is, if you wait for permission, some things will simply never happen."

"When you have hope in the future, you have power in the present. And when you lose that hope, your dream goes with it."

"Never plan for victory and defeat in your mind at the same time."

"This wasn’t some kind of stunt. This was a symbolic swim, and I needed to be courageous. [...] Swimming in a wetsuit or drysuit just wouldn’t send the right signal."

"When you are walking up a mountain to attempt something that nobody’s ever tried before, and you pass people bringing corpses down, it becomes very clear that if you get it wrong, the consequences could be fatal."

"I’ve been swimming for 25 years, and I don’t think there is one swim that I have done where someone didn’t say beforehand, ‘I don’t think it’s possible’ or ‘You’ll never make it’. If someone tells you that you can’t achieve your dream, don’t waste good time arguing. Walk away and do it."

"Don’t look for other people to validate your dreams. If it feels right, just go for it."

"No matter how tough my day has been, when I dive into the sea, the world seems perfect."

"There’s a fine line between bravery and stupidity, which should never be crossed."

"I always tell young swimmers: 'Practice things until you can't get them wrong. Not until you get them right.' There's a big difference."

"Law taught me how to argue passionately and rationally. That’s key to being a successful environmental campaigner. If you are too emotional you run the risk of turning off policy makers. And if you can’t present your arguments rationally, no one will listen to you."

"When I can’t decide which path to take, I have a meeting with the 75-year-old me. That person usually knows what to do."

"If you have a passion, follow it. It's the best barometer of what you will be good at. And choose a career that you enjoy – the extra money of a job you detest isn’t worth it."

"I tolerate cold water. Anyone who says they love swimming in freezing water is either lying or has never done it."

"I think it foolhardy to predict the absolute limits of human endurance."

"Too little confidence, and you're unable to act; too much confidence, and you're unable to hear."

"I look for swims where I can carry a powerful message. No message, no swim. I don’t get wet now unless it’s for a reason."

"I’ve swum through some very cold and rough seas. I think that’s made me more determined than the average person."

"As a pioneer swimmer, you've got to be willing to fail and try again. The point isn’t to learn to fail, the point is to learn to bounce back."

"There's a tyranny in perfection. Just do things to the very best of your ability. Then move on."

"My mind has to be ready. My body also has to be ready. But even more important, my heart has to be ready. What I mean by that is for the swims I do, I must have a burning reason."

"Being the first to undertake a swim is exponentially harder than going second. You don’t know what will happen. The fear can be crippling. It’s much easier to go second. You know it’s possible. But the world is divided into pioneers and followers. You are one or the other. I prefer to be a pioneer."

"The trick is to make fear your friend. Fear forces you to prepare more rigorously and see potential problems more quickly."

"To do anything worthwhile, you will face periods of grinding doubt and fear."

"You must not dither - swim like you're running through a minefield."

"You don't know pain until you've had a stalactite in your cock."

"If we pass on an unsustainable environment to our children we have failed them."

"There’s nothing more chilling than swimming across open sea, where recently there used to be a solid glacier."

"A thought came across my mind: if things go pear-shaped on this swim, how long will it take for my frozen body to sink the four and a half kilometers to the bottom of the ocean?"

"There is nothing more powerful than the made-up mind."

"We made fracking a civil rights issue. Because that is what it is. We all have a right to a healthy environment and to clean water. And so do our children."

"Unless our children have been into nature, it is unlikely they will care about it when they grow up."

"Everywhere water is under threat. It is our most precious resource. And there is no alternative to it."

"The right to have our environment protected for the benefit of present and future generations is our most important human right."

"Sometimes the moments that challenge us the most, define us."

"The English Channel is the perfect stretch of water to truly test the human mind."

"These are areas of unparalleled natural beauty to be handed to our children undisturbed. We are merely custodians. You would not build a toll plaza and an administration block in the Grand Canyon or next to the Victoria Falls or within any other World Heritage Site.”"

"A healthy ocean is an ocean with sharks. Take away an apex predator and it’s like removing the lions from the Serengeti. It won’t be long before the gazelle, zebras and wildebeest have multiplied and eaten all the grass. And when the land is laid bare the grazers will starve to death. Predators are crucial for a healthy ecosystem – be it on land or in the water."