You can go much deeper than 10 fathoms without supplemental oxygen, half the people reading this right now could do it with some training.
The world record is 117 fathoms on a single breath.
Free divers are a bit crazy...
No, just brain damaged from oxygen deprivation
How do they go back to the surface without fainting from decompression?
They're only down there for a very short time and they don't have a lot of nitrogen stored in their lungs, so decompression sickness is usually not an issue. I think there have been a few cases, especially with repeated, very deep dives. But nothing you have to worry about as a normal hobby freediver.
Passing out at the surface is quite common though, but not due to decompression sickness. It's the lack of oxygen that can happen when you have learned to completely ignore your urge to breathe and then stay down for too long. The reason why you pass out at the surface and almost never at the bottom, is because the water pressure compresses the air in your lungs. At a depth of 10 meters (30 feet), four liters of air in your lungs are compressed down to two liters. This is basically "concentrated air", which contains "concentrated oxygen". If the air is compressed to half the volume, it's like having twice as much oxygen in it. Then, as you ascend to the surface, the air in your lungs expands again, turning the concentrated oxygen into regular oxygen and then it's just not enough anymore and you pass out.
That's why it's recommended to always have someone with you who stays at at the surface and who can step in if you pass out, keeping your head above the water. It has never happened to me, but I'm really a beginner and I still have an urge to breathe that forces me to go back to the surface after a short while.
I need supplemental oxygen at less than 1 fathom under water, if I stay there long enough...
I highly recommend using compressed air over oxygen. Nitrox 100 (pure oxygen) becomes toxic below 5 meters...
1.6 bars partial pressure Oxygen is considered unsafe / hazardous.
Nitrogen also becomes toxic, requiring you to substitute it with helium (or hydrogen).
Interesting talk on the subject: https://youtu.be/skL5EQa8DFY
It's why I'll always remain happy with recreational diving at depths less than 40m :) Tech divers are a bit crazy imo. Sure, there's nice views to be had (if you bring a lot of light), but it's not worth the risk for me.
While we're at it, 20000 leagues under the sea is the distance they travelled, not the depth
For scale, 20,000 leagues is almost 9 times the diameter of the Earth
How many fathoms do you have to go before even death may die?
You're thinking of eons, which stand for time. But I like where your head's at
'bout tree fiddy
"Dammit, monster! Get off my lawn! I ain't giving you no tree-fitty!" It said, "How about just two-fitty?" I said, "Oh, now it's only two-fitty!! What?! Is there a sale on Loch Ness munchies or something?!"
1 fathom = 1.8288 metres. Yeah, I get why it's funny now.
What's so funny about 1.8288m? I don't get it.
your mom and I 1.8288m'd last night
I can't fathom how you'd find that funny.
And for people who don’t know how big that is. It’s about the height of a slightly tall man
Unfathomably based
The end of that reads like the grim dark of the 40k universe there is nothing but war
I read that as Just Poised on Things and thought it was very fitting.
It's 6 fathoms deep not 5 fathoms where you're experiencing two atmospheres, and that's absolute not gauge, so 1 atm higher than ambient.
Retard units at its finest. Why simple when it can be difficult.
For every 10 meters of water, hydrostatic pressure increases by one atmosphere
Wood Hole Oceanographic Institution
For every 33 feet (10 meters) of saltwater depth, pressure increases by another atmosphere.
It's less the result of a sensible system of units (like how 1 L of water ideally weighs 1 kg), and more fortunate happenstance in this case.
The formula for hydrostatic pressure* is:
∆P= ρ·g·∆h
where ∆P is the difference in pressure across the difference in height ∆h, ρ is the density of the liquid (~1000 kg/m³ for water, slightly more for sea water), and g is the acceleration due to gravity.
So the reason it works out nicely is because g is a little bit less than a nice factor of ten (9.8 m/s²), and the density of sea water is a little bit more than a nice factor of ten (typically 1025 kg/m³), and 1 atm also happens to be almost a nice factor of ten (101,325 Pa). That's why the difference between the approximation and the actual* is less than a percent.
*This assumes a constant density of the liquid, which for water is reasonable, however different depths can have different salinities and temperatures in layers which change the density by less than a percent. Additionally, this assumes a constant acceleration due to gravity. At depth, the acceleration due to gravity can be higher, but this also has an effect that amounts to less than a percent even at the deepest point in the ocean.
ewww standard atmospheres. Use kilopascals like the good lord BIPM intended
And then some nerds with a cool camera robot get down there because they want to poke dead whales with shit and see what happens
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