Koh Tarutao is one of my favourite Islands in the world. It has everything – quiet stretches of empty beach, a thriving ecosystem, an interesting cultural history. But there’s one thing that I like above all else about the island – The Crocodile Cave.

The friendly ranger man informed Freddie and I of a cave up a river that few people explored. It was known as the Crocodile Cave because it used to be infested with the things, but apparently there were no longer any living there… Either way we couldn’t turn down the opportunity.

We wandered down to the sleepy shore of the river, where a couple of locals were snoozing under a tree. They produced a kayak from a bush and slid it into the water, giving us some pretty vague directions. “Stick to the left an hour and you’ll be fine. But don’t get lost.”

We hopped in and began to paddle.

The river was a huge sweeping body of water, overwhelmed on both sides with dense mangroves. As we paddled we realised why the locals had been so adamant we should stick to one side. Without doing so it would be easy to get lost in the tiny tributaries that disappeared in every direction. We would peer into them as we paddled to see pathways fading into a maze of mangrove, where you could be consumed forever.

As we slowly paddled we drifted past some beautiful karst rock formations, but other than that it was only mangrove. We didn’t see a single soul or sign of human existence. The beauty and peacefulness of the river was mesmerising.

Eventually we reached a point where we could go no further, the river faded into a mass of foliage impossible to penetrate. A calm bay surrounded by rock, with the sun spattering gently on the water’s surface. This was the entrance to the Crocodile Cave.

Like Indiana Jones and one of his sidekicks, we tied up our kayak to the mooring and jumped on to dry land. There was a barely existant path into the jungle, over bridges of rotting wood and loose rocks that crumbled into waters below. But eventually we found it – a large dark opening in the side of the cliff with a turquoise pool of water at the entrance. A flimsy wooden platform led us inside where we came across a massive makeshift plastic raft. There was a huge rotten rope attached to the wooden platform that went through a loop on the raft and then entered the pitch black water on the other side, slowly disappearing into the depths of the cave.

We hopped aboard, beginning to feel the murky drip of fear creep down our backs. The raft was slippery with filth and slime. One wrong move and you’d be overboard, into the unknown darkness of the potentially crocodile infested pool. But we overcame the fear, and began to pull.

Yanking the rope between my hands we began to move slowly into the depths, gliding along the lifeless ebony surface. Freddie shone the only light source we had – a head torch – to reveal the route as much as possible. The darkness became oppressive as we got deeper, the light from the entrance disappearing quickly around a corner. Using our hands to navigate around stalactites and stalagmites that broke through the water like monstrous ogres. Bats were inches above our heads, chattering as they clung to the ceiling, or swooping and flapping around us as we disturbed their slumber.

The journey was only eighty metres, but in the darkness it felt like a mile. As though we had entered a new realm of existence. A realm where time is just a myth. Fears abounded in our minds. What if the rope broke? We’d be lost in this dark watery cave until the sleepy Thais on the shore noticed we were gone and searched for us. What if there was an earthquake and the entrance was blocked? We’d be stuck inside living like savages off the bats we can catch and the insects we could scrape from the walls. Eventually the torch would fade and we would no longer recognise each other’s faces, and the hunger might take us to places of unimaginable horror. What if there were things in here? Creatures that had evolved – once human or reptile, now just blackened souls out to eat anything they can get their mutated hands on……

Fortunately the raft touched a surface. A wooden platform, covered in grime but still intact. We tied the raft up, extremely carefully, and hopped on to dry land, relieved beyond belief.

But the fear was still there. We were eighty metres into a pitch black cave and wandering around. The head torch our only ray of hope. There were huge stalactites cascading from the ceilings, and stalagmites millions of years old commandeering attention from the middle of the massive open tomb. We felt like pioneers, lucky to see this astounding natural world before it gets developed and tourists are led in trains with a guide at the front brandishing a list of rules. We could witness the raw cave ecosystem – bats on the ceiling bringing in precious fuel, feeding the plethora of insects and arthropods with their guano. It was amazing.

But terrifying. It didn’t take long for the fears to creep in again. There were branches of cave in all directions, we could easily get lost. And the floor was sticky with clay, threatening to hold you prisoner with every step. We headed back to the raft, glad to be venturing once again towards the real world. As we pulled ourselves along the rope, the bright light of the entrance within our grasp and the sunlight nearly on my face, I imagined a creature – half man, half reptile – watching us and cursing with screeches and howls on the sticky clay floor. For he had missed his chance. We had survived the Crocodile Cave.