People ask me, why oceans? It's simple. They not only need protection, they deserve it.

The oceans cover over 70% of the Earth’s surface. We rely on them entirely for our survival – and the amazing creatures that live in them now rely on us for protection.

My decision to become an ocean advocate didn’t happen all at once. It began with the stories of exploration I loved as a child, and in the flights of imagination sparked by the world maps my father hung around our home.

It grew along with my sense of justice while I read law at the University of Cape Town, at the end of the Apartheid era. I had the privileged of being taught by a number of great South African icons, including Nobel Laureates and struggle heroes. I will never forget the thrilling moment my law lecturer held up a copy of the country’s new constitution, which was busy being negotiated in those heady times. It remains one of the world’s most progressive constitutions.

Then there was the sense of achievement I felt after my very first Robben Island swim at just 17 years old. It taught me that finishing a job gives you the power and the energy to go on to even bigger things.

Most importantly, it was in the way the natural environment influenced my development. I was awed by my first experience of real African wilds. I was awed in a different way in the Southern Ocean, when I found myself swimming over a graveyard of bones at Whaler’s Bay. I remember my father telling me about the first British atomic bomb test; when he held his hands over his face he saw his bones silhouetted as if it was an x-ray. If this is what a nuclear explosion does to us, I thought to myself, imagine what it is doing to the environment?

I began swimming in vulnerable ecosystems to draw attention to the impact of our actions on our oceans. I saw enormous chunks of ice slide off Arctic glaciers. I swam over bleached coral killed by rising sea temperatures, and over the bones of whales hunted to the edge of extinction. I visited lakes high in the Himalayas where once there was only ice. I saw plastic pollution in the most remote parts of the oceans, and garbage piling up so thick on city beaches that you can no longer see the sand.

I’ve witnessed drastic changes in my lifetime – changes that have come about because of our actions. I soon realised that it would require a different kind of action to bring about the changes needed to protect our vulnerable natural resources. And so I began talking – to national and citizen leaders, to policy makers, environmentalists, scientists and the media. Soon I was travelling more than I was swimming; people started calling what I do ‘Speedo diplomacy’.

I’ve been privileged to be a part of some positive changes. And to share my stories so that people realise that we all have it within us to make a difference.

I’ve shared my dream of oceans that are abundant with life, full of dolphins and whales, of penguins and sea birds, of turtles and manta rays. I’ve shared my belief that we can restore the health of the oceans; that it’s up to every one of us to protect our future.

Why do I do what I do? I do it because I believe in protecting our fragile planet, in peace and in justice. I do it because it’s right. I do it because our souls need nature. And I do it as much for nature’s sake as for ours.