Another water pressure question

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erakor

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I've seen several threads on this but they get complicated quick.

Trying to get a simple answer to real world problem.

Person drops item down hole and needs to retrieve it. Hole is 120 feet down until you hit water. Water depth is approximately 60 feet.

So 120 feet down hole + then another 60 feet water to reach bottom & retrieve item. Please without too much flaming discuss risks and suggestions.

Thanks in advance.
 
Since you'd barely feel the difference between sea level and 5000' elevation, I'd say it's pretty safe to ignore the 120' of elevation loss before you get to the surface of the water.
 
I would have thought the distance from the top of the hole to water level is irrelevant as it is the pressure of the water that you would need to worry about.

If the water level is at sea level then just go with normal dive tables etc. If it is significantly above sea level then adjust for that as appropriate.

60 ft / approx 20m shouldn't be too much of a stretch for AOW divers. (assuming access to the waters surface is practical i.e. no climbing equipment needed to get down the hole - that would create a bunch of other safety issues).
 
Depending on the size of the hole and if the object your looking for is metal, why not go to harbor freight and buy a big magnet and 200 feet of rope?
 
I would have thought the distance from the top of the hole to water level is irrelevant as it is the pressure of the water that you would need to worry about...

Probably true unless it is a high precision physics exercise. In order to calculate the effect of atmospheric pressure we would need the current elevation and barometric pressure. To get that precise you would also need the density of the water and temperature. The pressure difference due these effects would be less than could be expressed at 0.1 PSI precision. Totally irrelevant from a diving perspective.
 
The 120' doesn't matter as far as the diving goes. It's only really relevant as it presents a challenge, as the the OP described it as a hole. Climbing down with the gear on your back is not advised. You'll need some gear to lower the dive gear down. Nothing real fancy needed, but you'd want to avoid banging the gear off the side, so you may need a frame and pulley to center in the hole. Then, of course the diver needs to get down safely, so a climbing line of some sort would be wise. Diver would need to be able to remove gear from the rope, don, dive, retrieve item, doff, secure gear to rope, climb up, then retrieve the dive gear. Don't want to lift the gear before the diver is out of the hole in case the gear should fall.

Or, just call Lassie and tell her that Timmy fell down the well.
 
You would have to rappel down with your gear on, the tank and weights could be lowered separately. Then you would do the dive and try to recover the object. Third, you would have to remove your gear and ascend back up. You would also probably need a winch for the tank and weights. I used to spelunk with my father as a teenager and I have been diving for the past two years. So I have a little experience with both sports. This would not be my first choice of trying to combine them.
 
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