I’ve just completed the first long-distance swim in the seven Seas of the ancient world. I’ve experienced some things I will never forget. And seen some things I wish I could erase from my memory, but which will haunt me for the rest of my days.

I will never forget the people I met along this journey, the literally hundreds of people from all walks of life who helped us and supported us and jumped in the sea to swim with us, just to be part of this mission, just for their love of the sea.

And then there are the things I would rather forget. Such as the sea floor under me as I swam the Aegean, which was covered with litter. I saw tyres and plastic bags, bottles, cans, shoes and clothing – but absolutely nothing that qualifies as ‘sea life’.

Turtles and jellyfish – but where were the sharks?

In the Arabian Sea I swam through vast shoals of turtles, which was spectacular. They do belong there. But so do many, many other fish species, and those were nowhere to be seen.

I never saw any fish bigger than the size of my hand, in any of the seven Seas. The larger ones had all been fished out.

The Black Sea was full of jellyfish. This is not a good thing, because they don’t belong there – they were brought in with the ballast on visiting ships and wrought havoc on an ecosystem that was already unbalanced.

In the entire four weeks I did not see one shark, anywhere.

As I was about to jump in the water for the Red Sea swim I asked the boat’s skipper whether I should keep a look out for sharks. He told me not to worry, because the sharks have all been fished out. That’s exactly what does worry me. A healthy ocean is an ocean with sharks.

Suddenly, the Red Sea came to life

But I did see something astonishing in the Red Sea. It was when I swam through a Marine Protected Area, and experienced a sea as it was meant to be: rich and colourful, teaming with abundant life.

And then, just two kilometres on, outside of the protected area, the picture changed again. There was no coral and there were no fish. It looked like an underwater desert.

If I had needed more proof that Marine Protected Areas really work, that was it. Everything I knew about how MPAs allow marine life to recover, how they protect and restore fish stocks, how they provide income-generating livelihoods for local people, how they boost ecotourism and ensure long-term sustainability, was all there in front of me.

Many of the people I met along the way have experienced it too. They have seen their seas changing. They know that there is a serious problem. And they have seen that the problem is reversible, IF we take urgent action and create Marine Protected Areas.

Thinking ahead

There’s a reason we ended our final North Sea swim at the Thames Barrier. It’s a highly symbolic example of foresight and visionary design. When it was built 30 years ago, its engineers had no idea how crucial it would be. They thought it would be used two or three times a year.

But this last winter it was used 48 times. Where would London be today without the Thames Barrier? In a word: underwater.

I don’t want to imagine what the world will be like in 30 years time if we don’t protect our marine resources today.

The world’s waters are changing. The seas and oceans are in a state of crisis. And we rely on these seas and oceans – all of us on this planet, wherever we live – for our very livelihood.

I am well aware that the world is caught up in a number of serious global political and humanitarian crises right now. It is certainly not my intention to trivialise any of these. But in focusing solely on the current state of global hyper-conflict, we run the risk of losing sight of something that is going to affect our children and grandchildren.

Protecting resources fosters peace

The biggest risk the world faces right now is what is being done to the environment, and a large part of that is what’s happening in our seas.

When Desmond Tutu came to wish me well at the outset of this expedition, he reminded me of something fundamental. He reminded me that so many of the world’s conflicts are over resources. When we fail to protect our resources, we set the stage for conflict. But when we protect our resources, we foster peace.

I dream of a peaceful world of well-managed Marine Protected Areas, protecting our coastlines and extending across our high seas. Of abundant oceans teeming with fish, big and small, with turtles and whales and sea-birds. Oceans filled with sharks.

Now is the time to make that dream happen. To reverse the rampant devastation of our marine resources, to provide them safe havens that allow them to regroup and recover.  Too many species are dying out, hunted to near extinction, slipping through our fingers, like sand.

Let’s stop fighting. And start giving our seas a fighting chance.

Lewis Pugh is an ocean advocate and a pioneer swimmer. In 2010 he was named a Young Global Leader by the World Economic Forum and in 2013 he was appointed Patron of the Oceans by the United Nations Environment Programme. http://lewispugh.com

This article was originally published on Lewis’s blog.