Ever wondered what the inside of a Cornish cliff face looks like?
Neither had we, but that's why we're not members of the Carbis Bay Crew.
This group of intrepid thrill-seekers have been quietly working their way through the most inaccessible parts of the Southwestern coastline for a few years now, using a combination of high-tech equipment and old-fashioned daredevilry to explore the hidden caves of Cornwall.
And they might well have found their biggest discovery yet, in the smallest of places - as you can see in the video below:
Burrowing into a cliff face close to the seaside village of Porthtowan, they found themselves a tiny hole and ventured in - 200 metres later, they revealed ancient tin mines that once dotted the entire south-west of England.
Shot using GoPros and drones, the footage they captured is nothing short of outstanding. The explorers found themselves chest-deep in sea water, squeezing through tiny spaces known as adits.
Mark Thomas, who shot the footage, explains the idea behind the expedition: "We basically went down to explore a new hole that we'd found in the cliff and what we found was pretty spectacular. These are old tin mines.
"I think they would have been drainage adits dug down the back of the mines and out towards the sea. There's literally thousands of these and many of them have probably been here since the dawn of time. The Bronze Age effectively kicked off here.
"There are so many of these old mines and holes wherever you go in Cornwall and we just enjoy going where no one else has before."
Mark, 40, is a pyrotechnician by trade and delights in showing off the social history of Cornwall alongside the natural beauty of the coastline that is well documented.
"We've got about 30 members from all different walks of life and some of the things you discover are unbelievable. In Porthtowan we were able to get 200 metres inland through the adits, under the farmland and practically under the village itself," he says.
"Bits of it are flooded so it's like wading through a lake but their some really interesting sights down there."
Crawling through the cliff faces into the remains of tin mines is surprisingly legal, though not necessarily encouraged. "Everybody has their own reason for doing it. We've got history buffs, people who like the danger of it - geologists, etc," says Mark. "We see stuff you wouldn't see just going for a walk. We've got a lot of experience with the ropes and safety side of it but it is dangerous.
He continues: "It's all public land and totally legal. We take precautions, just like you would with an extreme sport, I suppose. It gets the adrenaline going. We film most of what we do to show it off to people who aren't lucky enough to be able to do what we do."
The results are staggering. "It's cool to think that this whole landscape lies behind a small hole in the cliff face," Mark concludes.
"The coastline is changing all the time in Cornwall and you never know when it might be gone. We want to preserve that."
Words: Mike Meehall Wood