The rumours have swirled around conservationists in Peru for over a decade, a secret slaughter that the world is almost completely unaware of, a brutal practice of slaughtering dolphins for shark bait.
But nobody has ever been able to get close enough to prove the killing in Peruvian waters - until now.
After 9 months of careful negotiations by our fixer we were given the call with one week's notice. At home with my young family in Brighton I rang cameraman Alejandro in Buenos Aires. It was now or never.
We dropped everything and flew to Peru. Arriving at the port at midnight, we were illegal stowaways, ferried on to our boat.
Our hearts sank when we saw the vessel, a tiny 30 foot boat, with just a cramped corner and 4 bunks carved out in the bow. Conditions were grim. The sleeping arrangements are tiny, four bunks for six people, and the space between too small for more than one person at a time to stand.
The first task of our journey was to get the bait to catch the sharks. The pigs of the sea is what the fishermen called the dolphins, "chechos" and soon enough the cry and the crew ran to the deck. The dophins had been spotted riding along with the boat, meaning it was time to go hunting.
Crouched by the gunwale close to the harpoon, I am dizzy with conflict; excited, relieved and yet sickened that after two years of preparation, planning and incredibly complex logistics, we are about to film something that has never been filmed before.
This adrenaline is an addictive buzz that investigative journalists so often get when they know they are about to capture something otherwise hidden to the rest of the world. I have done this work for years, but never filmed the killing of a dolphin.
This is one of the most intelligent animals on the planet - highly developed, socially complex dusky dolphin, an animal who has chosen to come and bow ride a boat just for the fun of it. I defy anyone not to be moved by their grace, and beauty.
The captain takes up the harpoon. He waits, watches and throws. Silence, then a cry goes up.
The line goes taught under the boat. The boat throttles into reverse, 30 yards distant at the end of the line a dolphin is thrashing wildly on the surface, flipper moving quickly amidst a growing cloud of blood in the choppy waters.
The men carefully pull the line in, closer and closer. The dolphin lies by the boat, belly up, shuddering. It's intestines spill out as it rises out of the waters.
The men drag it to the corner, it's beak still shuddering in it's death throes. With experienced ease, almost without blinking, one of the men sets to work slicing the fins of the dolphin as it swishes about in a puddle of blood.
The men have bait and we are underway again. A day later we arrive in the shark fishing zone, our 600km trek south has brought us to the narrow temperature gradient where the sharks should be waiting in large numbers.
A narrow escape
A few days later the captain agreed to drop us off to shore earlier than planned. They have 20 more days of this work ahead, but our work is over. I am relieved and excited at the prospect of dry land, and anxious to get our footage to safety.
As we slept and sailed, unbeknownst to us all, we had sailed into the middle of a collection of rocks. At first we celebrate the near miss, but then we hear the roar of rising thunder as the waves began to gather around us, frothing.
A huge wave sucks the water out of the rocks before crashing down on top of us. A wall of water runs across the boat on top of us. We are all knocked off our feet, thrown from the bows with the wave as it rips off the rigging, the mast and smashes through the glass windows of the wheelhouse at the aft of the vessel. We lurch from side to side. I managed to pull my soggy iphone out of my pocket and call our fixer.
The boat is on the rocks, the crew desperately trying to ply us away before the next set of colossal waves turn the boat over.
A coastguard is summoned out of bed via our fixer and a hefty encouragement fee.
However, foreigners on a fishing boat with lots of luggage in the early hours spells narco-trafficker in Peru. Jail awaited us, albeit it on dry land.
To our great relief, the engine sprung to life, another soggy call was made to the coastguard to send him back to bed and another fee agreed. We pass round cigarettes, coke, painkillers, to celebrate our narrow escape. The captain's face is still bleeding from the window which exploded in his face from the force of the wave. We are battered and bruised, but we are safe. We head north and on to Lima and bid a quick goodbye to our crew.
Alive and kicking, our footage is stored safely on the hard drive, and ready to show the world.
Jim Wickens is an investigative journalist with the Ecologist Film Unit, Eco-storm. He gratefully acknowledges the support from the Pulitzer Centre on Crisis Reporting. His views do not reflect those of ITV News.