An old WW2 ammunition ship off the south cost of England was full off brass topped shells. Most had been taken by divers over the years and it was now very rare to see them, apart from a pile in one corner of the ship.

This pile of shiny brass metal was miraculous untouched and remarkably clean after spending years underwater and you only found out why if you swam near them.

Out of the murky darkness the largest eel I have ever seen snakes forward, without exaggeration this thing had a head the same size as a horse's head, full of jagged teeth. I could not see the body as it looped into the dark and deeper into the ship. No one got near those shells.

Turns out for years this thing had been guarding the shiny brass shells, slithering over them, making them shine. We found out at the bar later that he was famous in the area and many people went to the wreck just to see him. No idea why this giant creature was guarding them like a dragon and its horde, but some said eels are like magpies and like shiny things.

When I used to surf I spent a good deal of time underwater - whether intentional, or not. One day, I went out in surf that was absolutely massive (for me). It was 10 foot solid all day. Bigger sets. Serious stuff. And it was a very dark, overcast Winter's day. And raining. You couldn't see anything above the water, let alone below.

At this place, the bigger it gets, the further out on the rock shelf it breaks. So I was at least 200 m from shore when out of the gloom towered an absolutely massive set. Enormous. As big as I'd ever encountered. There were only a handful of other blokes out there. The wave was mine.

At this point I wasn't scared at all. No, I wanted to get the biggest wave of my life. So I tried. I got onto it but I just messed up the position of my feet, ever so slightly.

No chance of pulling out, so I tried to go with it. And that is when it happened. The scariest water-based experience I ever had. I fell off and this thing just took me to town. It lifted me all the way up and over the falls - I thought I was OK, but no, it was just beginning.

It just kept pushing me down. Further and further. My ears hurt (badly), it was completely dark, cold (even in a wetsuit) - I came to rest on what seemed to be a very large, smooth rock (I could feel it with my fingers whilst I was pinned firmly to it).

I was held there for what seemed like an eternity. Maybe 10 seconds. But then I could sense with my feet a ferocious current that seemed to stop at the edge of the rock - it was trying to pull me over the ledge and DOWN. I could hear it. At this point I was panicking. Seriously.

I can't quite remember how I escaped. I have rarely been that scared in all my life. I made it to the surface. I really thought I was going to pass out. I can't remember much more but I must have paddled in so fast other people noticed. They came to see what was the matter. I just sat on the beach. I could not even talk. I'm getting the chills even reading my own recollection.

You can dive in manmade lakes and check out what's left of old flooded homes and communities. It's pretty dark and spooky down there no matter what, especially when you think of all the big fish swimming around that are barely silhouettes until they're close.

The creepiest thing, by far, is finding cemeteries 100 ft + beneath the water in the dark, eerie quiet.

I dive myself but heard this story from a fellow diver.

In 2010 a man took a test drive in a car with the salesman. He drove the car off the pier into the sea and drowned. The salesman managed to escape by breaking the window and swimming to the surface. The divers were dispatched to retrieve the other man's body.

Simply through working in marinas at the time I was able to be part of the conversation with the diver in question. When he got to the car he said the man was still facing forward, hands on the steering wheel, eyes wide. He'd been there a couple of hours now. Where it gets creepy is when the diver opened the driver door, this combined with the smashed window caused the currents to flow through the car and the man's wide eyed head turned around slowly with the force of it to face the diver.

I dropped my goggles and was trying to reach down in the river and grab it but I pulled out a sheep skull by its sockets. Wasn’t as creepy in hindsight but 10-year-old me was scared.

My dive master that told me once he was diving somewhere and found a full skeleton wearing diving gear with the air on the tank turned off pretty deep down. If I remember correctly they said they reported it to the police and it was found out the man's wife turned off his air while they were on a dive in order to do him in.

I once went diving in Port Elizabeth, South Africa, a popular diving spot indeed.

We begin diving and we are quite far from the shore, there’s a cool looking structure under us, we swim towards it to get a closer look and I just start getting this cold cold cold cold feeling running through my body. That’s when a shark appeared and I literally pooped myself from fear.

I used to do a lot of night dives hunting for lobster off the coast of California. We’d start at 9 or 10 at night so everything is obviously pitch black besides where we were pointing our lights. Every so often I’d get this unshakable feeling that something big was watching or following me. Sometimes I could quiet that part of my brain and continue with the dive. Other times I couldn’t shake the feeling and would end the dive after a few minutes. It’s a hard feeling to describe but I guess I’d compare it to being in a haunted house but 50ft underwater in complete darkness.

When I used to live on the coast, some buddies and I would take regular fishing trips out to the oil rigs. We would always have some lines out and a few would dive down and try to spear some mangrove snapper or cobia. Once while I and two others were diving down checking out the structure we decided we needed to move due to lack of life around the rig.

We all get back in the boat and as one of my buddies is reeling in a line we had a red snapper baited on.. an easily 8-10ft tiger shark starts chewing on it right behind the prop, so close I could have poked his eye out. The idea that massive animal was in the water so close to me and two of my friends but no one saw it is terrifying. I bet he was watching us the whole time.

One of my first dives was in nightmare conditions. There was a strong current and so much sand/debris everywhere that visibility was at about 12 inches. For some reason the dive master was like "it'll be fine once we get below 40 feet". We started descending on a guide wire and after getting to about 55 feet my brother and I (who were dive partners) could not see anyone else in the group.

We waited at the bottom of the wire for 10 minutes and after no one showed up we started to think that the rest of the group would be waiting on the surface. We came up and 1 guy from our group was at the buoy looking confused and the boat was gone.

Turns out there were so many problems that the boat drove away so that the waves wouldn't throw it on top of us but there were such large swells that the boat couldn't relocate us. We floated for about an hour before finally getting the boat's attention and being picked up.

By far the worst motion sickness/dehydration I've ever experienced.

I had a dive buddy go OOA (out of air) on me while we were exploring a wreck in the St. Lawrence River. Thankfully this was a no-deco dive in < 100' of water and we weren't actually inside the wreck but the part that made it particularly challenging was that the wreck was right in the middle of the shipping lane (where really large freighters travel), with really high current, so we couldn't just make an easy ascent to the surface.

We had to navigate along a series of lines (pretty thick rope tied off on some good anchor points) that had been laid out to give divers something to hang on to so they could pull themselves against the current on the path to the wreck, and stabilize themselves during the swim back to the anchor line.

We were making our exit and everything was going fine, he was on my long 7' hose out in front, and I had a hand on his knee so we were keeping in good contact. Then for one moment I let go of his knee to deal with some gear and in that split second he came off the line and got caught in the current, ripping my regulator out of his mouth in the process.

I saw him manage to grab hold of another of the lines downstream and he was hanging on for dear life, completely inverted, in a shipping lane, with no regulator in his mouth and no gas in his tank, flapping in the current like a flag in the wind. I bolted towards him as quickly as I could while still maintaining my own safety, and gathered up the 7' of abandoned hose and regulator along the way.

I caught up to him and manage to get the regulator back into his mouth, but since he was inverted, it went in upside down and as a result didn't breathe like it should. He fixed that himself, but slipped off the line he was holding onto in the process. I managed to get a hold of him, but not without having to let go of the line myself, so I ended up hooking both of my feet around the line to keep us both in place. Somehow I managed to pull us both back down to where we could grab hold of the line.

It was at this point that another diver in our group saw what was going on and assisted and from there we were able to get back to the boat without any further incident.

I had to make an emergency ascent from 120 ft while wreck diving off the coast of North Carolina. The longest 2 1/2 minutes of my life.

I was 30 meters below the surface in a small shipwreck. At one point my tank softly hits the ceiling and my jacket kept inflating which means I was quickly going back up to the surface which is really dangerous. I noticed something was wrong when I couldn't deflate the jacket. I had to quickly swim down with all my might to reach fellow divers but it was really difficult. Of course this results in consuming more oxygen. I had to stop the airflow from the tank to my jacket and then I was able to delfate it. I had to inflate it manually for the rest of the dive.

I was also diving with a group of beginners once and there was a lot of underwater current at one point. Eventually someone got sick and was going to throw up. He was about to remove his mask to puke but the instructor quickly swam towards him and stuck her hand on his mask. The guy had to puke in his regulator.

Oh and some other guy found a moray eel and pointed at it. He got bit.

I was on a wreck dive off Oahu down about 90ft with an ex-girlfriend and the owner of a local dive shop. The ex and I are experienced divers and we were all just messing around, checking out the wreck and the turtles nearby. There had been a group that was on the wreck but they had left as we descended, so it was just us three. About halfway into the dive another person shows up, alone.

He got the attention of the dive shop owner, and after furious scribbling on slates, the shop owner came over to us and wrote out “you both stay down and finish your dive, I’m taking him up”, and then turned to the other dude and gave the guy his octopus regulator to breathe from.

We didn’t really know what was going on so we had a perfectly lovely dive, got some good pictures, and ascended like normal.

When we got back on the boat we heard the story. That other guy was from a different boat and had been diving a totally different dive site. He somehow got separated and lost, and had somehow drifted about a mile away from where he went in. There was nothing else around in the direction he was going except Tahiti a few thousand miles away. Worst part is that the other guy's boat didn’t even realize he was gone and left without him.

If that guy hadn’t floated past our wreck, I don’t know what would have happened...the current pushes you away from land where we were, and since the boat didn't even know he was lost he would have been floating out for a long time before someone realized they had a missing diver.

My friend and I go charged by a mother humpback. Her curious calf had swum around us and we were between her and the calf. The two of us never saw it coming; we were watching the baby, but our third diver saw her coming. She kicked down and swam under us at the last minute. We didn't see anything until that 60ft freight train passed just underneath us.

That was an amazing experience, but also terrifying.

Coming up from a dive in Indonesia, didn't realize a sea snake was coming up for air at the same time until I surfaced. Everyone on the boat just started yelling SNAKE. I kept my distance and it went back down, but it freaked me out how close it was. If they hadn't have warned me I might have run into it. Did a second dive and saw the bugger again, he kept following me for a bit and that freaked me out.

Those snakes are incredibly venomous. Occasionally people even die.

I was in Belize for a multi-day diving trip with a girlfriend. This was her first dive trip after getting open water certified. We dove the blue hole and a few other spots and because of the depth and number of dives we had to do a decompression stop for 5-10 minutes or so at the end of this last dive.

During that last dive, my girlfriend was struggling with water getting in her mask and started to panic and we were between 45-60 feet down. I could see she was freaking out and pointing to her mask and slowly going toward the surface. I was trying to make signs to her that she had to stay down and to not go to the surface but it was really hard to communicate that.

At around 15 feet I had to physically grab her and start pulling her down. She had a little air in her buoyancy compensator which wasn't helping. I cleared any air from her compensator and just started pulling her down. It was really so scary. No one wants the bends.

When we finally got on the boat she thought I was just mad at her for not swimming with the rest of the group thinking I didn't understand she was having mask issues and didn't realize what I was trying to tell her.

Rescue diver in The Bahamas - diving in a submerged blue hole (the entrance is below sea-level) and a diver went missing.

After hour or two of searching, went back into the blue hole to see if there were any signs of him. Saw the glint of his watch and his arm sticking out near the bottom.

Start descending down to the bottom to recover the body. On the way down realized that the "bottom" was a school of sharks that must have been there for breeding. So many sharks that they blocked view of the actual bottom.

Descended into the darkness, grabbed his arm (couldn't stand to look at the body) and started ascending. The sharks followed. And were circling the both of us. Had to take a break at halfway at around 65 feet as to not get the bends. Scared out of my mind. Turns out he had been struck by a passing boat.

Partner lost his mind due to narcosis (nitrogen reaction) at 175 feet and very heavy current. Had to lead him all the way through decompression while clinging to a rocky cliff face. All the while I was trying to figure out at what point I would have to let him go to save myself.

Mine started scary but then turned awesome then scary again.

A friend and I used dive off Catalina Island, back in the mid 70's, to sift through the bottom for lost jewelry and stuff. The water was incredibly clear back then and made it easy to see the tiniest thing during the day, especially at noon. We were down one day and I was sifting through the sand when all of a sudden it went black and I was slammed hard to the floor, losing my mask and mouthpiece. I managed to find both, rolled onto my back to make it easier to clear my mask to see a pod of whales overhead.

It was amazing that one them displaces 10 feet of water with its fluke with enough force that it was like a truck dropped on me. Careful not to get between any of them, we got to touch them as they swam by.

Two weeks later we were out again and a shadow went over me. I rolled over to see the whales and watched a Great White going past. It disappeared in the distance then we called it a day.

A few years later we were diving and we had three orca swim by but they didn't seem to give us a second thought

Diving off of Pensacola, FL...thousands of moon jellyfish. One stung me pretty bad on the arm.

For non-divers, you don't see the color red the further down you go. So while the sting - which went all up and down my arm, turned red/pink all I could see was my arm turning black.

It was so freaky. When we finished the dive the boat captain said he had been doing that job for 20 years and it was the worst sting he had ever seen and that I was extremely allergic.

The scariest was being left behind on a dive trip in the Phillippines. After about 10 minutes of wondering what I was going to do, we saw the boat coming back and luckily was able to flag them down. It took everything I had not to strangle the guy in charge

Another time diving in Monterey I had a group of sea lions mess with me. They came to our area as we were very careful not to go near the seal rock jetty/ break water. Three of them started swimming around me which I thought was cool, then they started bumping into me and smacking me with the flippers in the head and back. The dive master saw it and tried to intervene but they took off.

The story is from a friend of mine who does night dives.

Here on the Brazilian coast there's a fish that resembles a shark, but it's considerably smaller, called "Cação". You have to hunt these things at night because they're sort of nasty in the open, but easier to shoot when in their coves.

So, my friend (Let's call him Regis) is about 1km from the coast, diving near a reef. This thing is massive and you have to go really deep to get to the slope with the coves. He is descending with a partner using cylinders for oxygen and armed with a reloadable harpoon gun, which is kinda heavy, making movement a tad slower. It's super dark in the deep during the night and too much light will alert the fish they're hunting, so they have to use flashlights that are weaker.

Regis said he had a feeling while descending, everything was off: the smaller fish were absent, there were no turtles, water was murkier than the usual. His partner stays back with the flashlight and he goes closer to the reef. Regis searches for the coves but can't find any with the Cação he wants, so it takes a while. At a certain point, he feels a shift in the water, like something big is swimming near him, just as the weak light from his partner shutters and goes out.

He doesn't know what to expect and goes into flight or fight mode, except he can't ascend too fast. He then tries to stay at the same level, but he has his back to the reef now. Then he cocks the gun with the harpoon and waits. Waits and waits, but he doesn't see anything in the murky night seawater, not even his partner's light. That had to mean one of two things: either his partner ran out of batteries, or he saw something and didn't want to attract its attention.

Regis finally decides to start ascending very slowly. The weird feeling he had got worse and turned into chills. As he's going up, he feels that same shift again and does not hesitate to harpoon whatever it was, but missed. He said he never saw something so big underwater and it swam fast. As Regis couldn't see much in the dark, he couldn't make out a proper shape, but saw that the thing went deeper near the reef. So he tries to go up as fast as possible and makes out to the boat, where his partner helped him up.

Turns out his partner warned him about it with the light, because he saw "something abnormally big" swimming at a dangerous distance, but couldn't get to him, because he felt watched by the thing. They both call it the blackfish, since they couldn't really see what it was. It's said to be as big as a man, about 1.7m. Regis lost the harpoon in the end.

Both of them still dive at night. It's a no-no for me, though.

Also, always dive in groups, guys: if something happens, you gotta have someone to have your back. You never know.

I used to teach canoeing lessons to Boy Scout troops at a local lake. Super small lake that's not very deep but the bottom was thick with vegetation. The water was "dark" so you couldn't see your hands in front of you for more than like 5 inches under the surface. There was a small clubhouse, an open pavillion, and a playground all on the property.

When doing lifeguard work in the water during a swim test, my sunglasses fell off my head. I dove down to find them and shit you not - I found a sunken, entangled hospital gurney at the bottom of the lake. It took a few people to untangle it but how the eff it got there was beyond me. Clearly it had been under the water for years...

I'm a commercial diver, and was once on a job cleaning a potable water reservoir. I'd been in other reservoirs before, but this was by far the biggest, at 40x80 metres. To get in you had to open a hatch in the ground (the whole reservoir was underground) and climb down a ladder. The hatch was in a corner, so when you were in the far corner of the reservoir, it was completely pitch black, and you just had to hope your light didn't go out.

I was about half way through a three hour dive when the batteries in my torch started going flat. I watched the beam get narrower and dimmer until it cut out completely. It's not a huge problem if you lose light, as you can just follow your umbilical back to the hatch.

But just as I started walking back, some obnoxiously loud banging started somewhere in the reservoir. I was the only diver in there, so it both confused and scared the crap out of me. Needless to say I ran back to the hatch as fast as I could.

I ended up getting my torch changed out and doing another hour in the water, but didn't hear the noise again. I still have no idea what it was, but the combination of my torch going out and loud banging coming from somewhere gave me a heck of a fright.

I’ve done a number of dives, and the strangest thing I ever saw was a large deep freezer with a heavy industrial chain wrapped around multiple times with about 5 cinder blocks attached. It was very very rusted and the deep freezer itself had to have been 30+ years old, probably more. This was about 90 feet deep just off Vancouver Island, Canada.

The situation gave myself and the other divers the heebie-jeebies. Logged the GPS and depth co-ordinates and notified the police. We were able to find out what was inside, since one of the divers had friends with local police. Ten porcelain dolls...

So, 3 days ago I went snorkeling off Mnemba island in Zanzibar. Everything went normal, and we start heading back. I grab my net bag and put my black fins, black mask, snorkel and black wetsuit inside.

Once back ashore, I grab my bag, jump off the boat and head to the rental office to return the equipment. At that point I feel my bag is moving somehow.

At first look, it seemed like a flat, black, worm squirming quickly. After rotating the bag, I realized I was looking only at the tail of an otherwise ~1m long black sea-snake, one of the most venomous reptiles I could find, trying to get out of the net.

How it got there, I have no freaking clue.