Pursuant to a common question that pops up in discussions of Pirates of the Caribbean, how deep could your skeleton go and still be intact? The flesh can be pulped for this discussion - its irrelevant.
Oh poo, I had this lovely reply typed all up for you with proper numbers and workings out and everything, but the hamsters ate it. 
From memory…
Greys Anatomy defines bone as having a compression strength of between 18,000 - 24,000 pounds per inch.
Water weighs about 0.036 pounds per cubic inch. (I think I remembered that right?)
I forgot how deep the carribean sea is… sorry, but bone would be quite happy at the bottom of it. But I guess you wanted to know about the integrity of an actual intact skeleton, right?
I’d reckon that cursed undead skeleton pirates would probably be ok. 
Cool! Thanks!
I will hazard a guess that your bones will stay intact at virtually any ocean depth.
For comparison, think of a solid chunk of homogeneous isotropic material: a cube of aluminum, say, or plastic, or rubber. If you subject that material to hydrostatic stress (pitch it in the ocean, in other words), it will compress, but it will not yield. This observation is the basis of the widely-used von Mises stress theory, where, for the purposes of calculating yield, the hydrostatically-induced stress is subtracted out from the stress state of the object. So if you throw, say, an eraser, or a glass paperweight, or a tire rim, or any other solid object in the ocean, it won’t squoosh out of existance.
The reason why I’m only hazarding a guess in this instance, though, is that a bone is neither homogeneous nor isotropic. Long bones, certainly, have inner marrow cavities (and are thus heterogeneous). Additionally, bones have a microstructure (which I assume is oriented along the length of the bone) and thus are anisotropic. Accounting for this is certainly beyond my ability to do off the top of my head (in addition to the fact that I don’t even know what the actual structure is).
However, my gut feel is that, first, any cavities in bone would be filled by water or water-like substance that is relatively incompressible, which would severely reduce the left-over stress that would induce yield (the von Mises stress, in other words). Also, my impression (sorry, no cite) is that bone is relatively tough and flexible: it needs to be, right? So it should be able to support a reasonable amount of strain (and stress) in any case.
While smiling bandit stated that flesh was irrelevant (great evil supercomputer tag-line there), zut’s reasoning applies to it too. Corpses sinking to the bottom of the ocean would arrive pretty much intact. While the pressure would prove lethal to an unprotected diver, that’s mostly due to humans’ need to respirate air. Demonstrations of deep-sea pressure in which styrofoam wig blocks are shrunk to a fraction of their original size work because styrofoam is filled with compressible air pockets. While a corpse’s lungs would collapse at great depth (or already be filled with water, and thus be unaffected), the rest of the body, being fluid-filled and incompressible, would not be significantly affected.
Incidentally, the James Cameron movie The Abyss illustrates the possibility of diving to extreme depths by breathing an oxygenated liquid instead of oxygen. The principle (and the fluid) are real, as is the demonstration of the principle shown in the film using a rat, though I believe human experimenters have found that breathing a fluid is too painful and fatiguing to be practical.
Calcium carbonate is unstable below ~4500 meters, so your bones (phosphate plus carbonate) will at least partially dissolve below that depth.
Interesting, I didn’t know that, and it prompted me to search a little further.
Apparently no human remain have ever been recovered from the Titanic (approx 4023 metres deep) according to this site:
“No human remains were ever found at the wreck site. The only explanation for this is possibly because the mud on the sea floor has an acidic level of PH 4! (That’s the same strength as the acid in your stomach)”
Anyone got any idea if that info is accurate? Applies only to the sea bed the Titanic lays in? Or how long it might take for PH4 to disolve bone?
(hey, it’s late, I just finished work, I am a sleepy bunny!)
Wrong ! There’s also various alien abduction scenarios that could explain the absence of skeletons.
Anything below pH 6.1 (the pKa of carbonic acid) is bad news for carbonates. At a given pH, the rate of dissolution depends on the ionic strength of the acid and the structure of the object being dissolved.
Fnar! 
So ok, lets see, the baddies in PotC can’t have been zombie/skeletons for all that long - Jack Sheppard was supposed to have been abandoned on the island just before they got the treasure, and he aint all that old, and I doubt they spent that much of their time on the sea bed when not trying to sneaky up on peoples.
Plus they were only actually skeletons in the moonlight - if the light had not pentrated that deeply into the water they would have been flesh, so the bone would have had some protection.
(As evidenced by the putting the bomb(?) in the rib cage of one skeleton then pushing him out of the moonlight so he couldn’t get it out again.)
Actually, just trying to find out what pH the Carribean sea is turned up this site which goes on about corals and such like…
“Scientists are studying the biodiversity of the microbial community found in the pelagic ocean and in association with the benthic (ocean floor) organisms, such as sponges and corals. Corals are found here in Florida and in Bermuda. They are found in shallow waters where they can stay at the ocean floor and still receive sunlight. Corals are formed by millions of tiny sea animals called polyps. Polyps take calcium from the sea water and convert into limestone (calcium carbonate), with which they make “houses” around the lower halves of their bodies. When they die, the limestone “skeleton” remains. As more and more polyps grow on top of each other, they form a coral reef. Corals thrive in warm, shallow water (60? F) and no deeper than 45 meters. The algae that grows there need the sunlight to do photosynthesis and provide food and Oxygen for the coral animals to eat and breathe. Some reefs are thousands of feet thick because they have grown as the sea floor sank. Reefs are found off the coast of Australia, in the Caribbean Sea, off the eastern coast of the Florida, in Bermuda, Japan, Hawaii, and other places.”
(bolding mine)
So I reckon our skeleton buddies would have been alright providing they didn’t stray too far underwater?
No, it isn’t: the pH of stomach acid is more like 1. Cite. I’m not sure about the pH of the mud. A pH of 4 might dissolve the minerals out of bone (vinegar does, and it has a pH of 3) but it’s certainly not anywheres near as nasty as stomach acid.
I don’t think many people actually went down with the Titanic. Most of the victims remained afloat, but froze in the very cold water. Many of the bodies were recovered. Some were taken back to be burried on land, others were reburried at sea - not necessarily at the Titanic site, and presumably many others drifted away, and were never found.
http://my.execpc.com/~reva/html3b.htm
perhaps the reason they have found no corpses at the Titanic is that there never were any to find.
I don’t think so–I’ve seen this picture, supposedly from the Titanic wreck site, in which a pair of boots marks the former resting place of a human body.
