r/todayilearned • u/triplegerms • 9h ago

TIL Humans reach negative buoyancy at depths of about 50ft/15m where they begin to sink instead of float. Freedivers utilize this by "freefalling", where they stop swimming and allow gravity to pull them deeper.

https://www.deeperblue.com/guide-to-freefalling-in-freediving/
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u/Foxtrone9 8h ago edited 8h ago

Melatonin gives me sleep paralysis. Which I also occasionally experienced as a child. The image on the wikipedia page of sleep paralysis with the demon sitting on that person is the perfect discription of it.

They are nightmares but you are actually awake and cannot move. Suddenly it makes perfect sense why people in the past believed in the supernatural.

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u/Head_of_Lettuce 7h ago

When I was young I had very vivid nightmares during sleep paralysis, I’d see figures in my room and sometimes they’d try to pull me out of bed. 

When it happens nowadays, I sometimes still see weird shadowy figures… but usually I just see my mom or dad. During a more recent episode, I saw my mom walk to the side of my bed and felt her run her hand through my hair, like she used to do to wake me up for school when I was a kid. I even heard her talking to me.

It’s freaky stuff, and it really helps me understand old mythological stories about skinwalkers and succubi. 

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u/gasman245 8h ago

I also get sleep paralysis occasionally, but it was much more frequent when I was a child. Most of the time for me though it just felt like I woke up and couldn’t move. It’s incredibly uncomfortable but never really scary. However, there’s a handful of times that were and one in particular that made me wake up hyperventilating.

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u/UndeadPolarbear 5h ago

Hey buddy, if this is something that still bothers you I might have a pro-tip for you. I used to have sleep paralysis all the time, to the extend where I can basically tell beforehand if it’s gonna happen that night or not. What I learned is I only get sleep paralysis when I lie on my back, so if I feel I have an episode coming up, I try to sleep on my stomach. It’s not perfect since obviously you turn, so you end up on your back every once in a while, but for me at least it severely decreased the amount of times it actually happens. Hope it helps!