Not necessarily, you wouldn't get crushed no matter how far you dive. The issue is oxygen. Theres a certain percentage of air that is oxygen. At greater depths this oxygen becomes poisonous under pressure. Divers use mixes of artificial gases and oxygen in certain tanks for deep sea diving. After 1800 feet, divers won't be able to breath. So they won't get crushed, just can't breath that deep.
At 6500 lbs per square inch I really don't think O2 is the more pressing factor.
Pressure increases with ocean depth
Submersibles are required for deep sea exploration. Here, the
Hawai'i Undersea Research Laboratory's Pisces V submersible prepares to dive to depths of over 4,000 feet (1,219 m) during a 2009 mission in the
Papahānaumokuākea Marine National Monument.
At sea level, the air that surrounds us presses down on our bodies at 14.7 pounds per square inch (1 bar). You don't feel it because the fluids in your body are pushing outward with the same force.
Dive down into the ocean even a few feet, though, and a noticeable change occurs. You can feel an increase of pressure on your eardrums. This is due to an increase in hydrostatic pressure, the force per unit area exerted by a liquid on an object.
The deeper you go under the sea, the greater the pressure of the water pushing down on you. For every 33 feet (10 meters) you go down, the pressure increases by 14.7 psi (1 bar). In the deepest ocean, the pressure is equivalent to the weight of an elephant balanced on a postage stamp, or the equivalent of one person trying to support 50 jumbo jets!
Many animals that live in the sea have no trouble at all with high pressure. Whales, for instance, can withstand dramatic pressure changes because their bodies are more flexible. Their ribs are bound by loose, bendable cartilage, which allows the rib cage to collapse at pressures that would easily snap our bones.
A whale's lungs can also collapse safely under pressure, which keeps them from rupturing. This allows sperm whales to hunt for giant squid at depths of 7,000 feet (2,100 meters) or more.
Titanic was long thought to have sunk in one piece and, over the years, many schemes were put forward for raising the wreck. None came to fruition.<SUP id=cite_ref-FOOTNOTEWard2012166_187-0 class=reference>
[180]</SUP> The fundamental problem was the sheer difficulty of finding and reaching a wreck that lies over 12,000 feet (3,700 m) below the surface, in a location where the water pressure is over
6,500 pounds per square inch.<SUP id=cite_ref-FOOTNOTESpignesi2012221_188-0 class=reference>
[181]</SUP> A number of expeditions were mounted to find
Titanic but it was not until 1 September 1985 that a Franco-American expedition succeeded.<SUP id=cite_ref-FOOTNOTEWard2012171.E2.80.93172_189-0 class=reference>
[182]</SUP>