Answers found on Ask Reddit
1. “I worked as a commercial diver for about 7 years in the UK and also some work in Europe.
I was working in Orkney, North of Scotland, on the fish farms. One time I swam down one of the bigger nets off Rousay and it was very dark, very overgrown, and I could see some weird shapes lying in the dead man’s sock as I descended. There were a few more dead fish than usual, maybe a hundred or so, but underneath them were lying three dead seals. Big ones. It was hard to make out because they were covered in fish but one of the seals had a big fucking chunk of it missing. And that’s when I looked up and saw a four foot tear in the side of the net. Fuck that. I was only a noobie at this point (fish farm work is generally the best way to start a diving career, doesn’t pay the best but you get plenty of minutes logged which helps for experience). I told the supervisor who said get out straight away. They sent one of the more experienced lads in after me and he fixed the hole sharpish and then rigged the seals up to be lifted out. Turns out the seals had been killed by Orca and somehow got through the net in a panic. Orca are quite common up in Orkney and are the only animal we were told you HAD to get out the water for if seen. Only one of the seals had a bite mark, the other two got caught in the net.
Not supernatural or anything but I remember a significant shiver running down my spine that day.”
2. “I dive myself but heard this story from a garda diver. In 2010 a man took a test drive in a car with the salesman and in a suicide attempt he drove the car off the pier into the sea and drowned. The salesman managed to escape my 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.”
3. “You can dive in man made 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.
My buddy likes to dive in lakes. He said the creepiest thing, by far, is finding cemeteries 100 ft + beneath the water in the dark, eerie quiet.”
4. “I got told a story once by a Maori Language teacher of mine during my time at High School. We didn’t learn much Maori, just listened to stories.
A dam in the Waikato, New Zealand had begun to have visible cracks in the concrete on the outside part of the dam and some drivers were organised to dive down and check the inside submerged part of the dam for damage on that side.
While they were down there, there was the usual debris you would find behind a man made wall which prevents the water from flowing as it would normally do if there wasn’t a dam there.
Turns out what they thought were large logs were in fact huge eels which had gotten to the size of logs due to being prevented from migrating to the sea, where they breed and die. So from being prevented from doing their natural life duties they just get larger and larger.
That would be creepy seeing eels deep down in the water just floating around…”
5. “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.”
6. “Got charged by a mother humpback, her curious calf had swum around us and we were between her and the calf. Two of us never saw it coming, we were watching the baby, but our third diver watched her come. She kicked down and swam under us last minute. We didn’t see anything until that 60 ft freight train passed just underneath us.”
7. “I had a 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 to murder him.”
8. “When living off 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.”
9. “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 metals was miraculous untouched and remarkably clean after spending years underwater and you only found out why if you swam near then.
Out of the murky darkness the largest moray 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 morays are like magpies and like shiny things.”
10. “When I was a kid swimming in the lake at summer camp, I dove underwater and I swear I saw someone in SCUBA gear hiding underneath the dock watching us. I told the lifeguard, but he wasn’t able to find anyone.”
11. “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 40×80 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. 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 shit 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 hell of a fright.”
12. “I used to teach canoeing lessons to Boy Scout troops at a local neighborhood lake. Super small lake that’s not very deep but the bottom was hella 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…”
13. “Not a diver, but heard from old divers that worked for the core of engineers, that There’s some huge catfish around the bottom of the dams. Like the size of vans.”
14. “My Granddad used to be on a crew that dove in the Zambezi River dam hen Zimbabwe was Rhodesia and he said there was 1 or 2 catfish in their that were so big they were eating some of the African workers semi regularly and would wait underneath the dam where they were doing repairs. It got so bad and the proved so difficult to hunt that they ended up just pouring concrete into all the little caves underneath to either trap them or force them to move away.”
15. “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 newbie 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. 10 porcelain dolls…”
16. “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.”
17. “I once went diving in port Elizabeth, South Africa where it is quite popular to see sharks.
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, and that’s when a shark appeared and I physically shat myself from fear.”
18. “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 shit 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 fucked 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 fucking 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 fucking 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 fucking heebie jeebies even reading my own recollection.”
19. “The story isn’t really mine, but 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 fuckers 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 harpoon gun (the kind that shoots the harpoon and is reloadable), which is kinda heavy, making movement a tad slower. It’s super dark at the deep during the night and 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 kinda long. 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 waves frenetically and goes off. He doesn’t know what to expect and goes on 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 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 partners light. That had to mean one of two things: either his partner went out of batteries, or he saw something and didn’t want to attract it’s 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 in 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.”
20. “Not a diver but, when I was surfing New Zealand’s west coast beach, I felt something wrap around my leg, so I looked down and it was fishing line. I tried to pull it up and then the line got heavy, I assumed it was a fish, but as I pulled the line closer it got really heavy and I began to sink so I hoped on my board and paddled closer to shore. I slid off my board and was in chest deep water, my friend came over cause he noticed something was wrong. We both pulled the fishing line in and we saw a large silhouette in the water so we dragged it to the surface and it was a dead body. There was a hook stabbed into his neck and fishing line wrapped around his face and dug into his skin. We brought the dude’s body to the shore and called in the life guards, then threw up due to the lack of his eyes.” 
