Underground cave explorer is stopped in his tracks and immediately leaves after spotting something on the walls

One of YouTube's most fearless cave divers is back in action to show us the harrowing reality of what you can find.

ActionAdventureTwins are the identical twin explorers - James and Edward - who share viral videos of themselves getting lost in some of the most dangerous caves in America.

In an upload from this June, one of the twins explores a cave which was requested by one of his commenters.

Viewers think they spotted someone's belongings left in the cave (YouTube/ActionAdventureTwins)

Whilst he didn't reveal his exact location, it would have most likely have been somewhere in the US, which doesn't really narrow it down, I know.

Now, the video description which read: "It's not worth it," is definitely a sign of things to come.

On first entering the underground cave, the content creator spots animal faeces on the floor and immediately regrets not 'bringing his gun'.

"I am so ill prepared, I got no knee pads or gloves, short sleeve shirt, what am I doing?" he said.

However, later in the video, the brother was stopped in his tracks after spotting some 'blood' on the rocks.

The YouTuber got out of there as quick as possible after spotting blood (YouTube/ActionAdventureTwins)

"I think that's blood," he said, "oh my god guys, I think there's actually blood up there."

That's when the cave explorer decided enough was enough and got himself out of there.

Viewers were stunned by his lack of preparation on such a dangerous solo-mission, as one person commented: "'Is that blood?' has to be pretty high on the list of questions you don't want to be asking yourself in the middle of a cave."

Another added: "No caving gear, no safety gear and all alone deep in a cave... This is a recipe for a disaster in the making with this guy..."

"This is a loose cave; highly dangerous for all professionals. You already know this information; try not to listen to the evil voices that told you to explore alone," warned a third.

"Every time you mentioned seeing more bear tracks, I can’t believe you kept going in further. Omg not safe, especially all alone.

"The blood freaked me out and then you mentioned that whatever was out hunting would be heading back in. Holy cow."

Meanwhile, others thought they noticed someone's belongings in the video.

They wrote: "That stuff on the ground at 15:42 looks very much like a smartphone on the left (partially obscured by rocks, screen dirty if facing up; might be upside-down) and on the right (the blue thing) what might be some sort of bag (perhaps for the phone; if it's a bag, it seems damaged), and left of the smartphone-looking object there's what looks like two AA or AAA batteries (next to a rock that's about the same length as the phone."

Well, it seems that fans of the explorer are hoping he takes better precautions next time.