For Frank Bowers, Normally we think of liquids as
incompressible, but they are actually very,very, very slightly
compressible at very high pressures. At a 7,000 foot depth, the
pressure in seawater is about 3,100 psi. The density of seawater
at this pressure is about 1.038 grams/cubic centimeter (assuming
the temperature is about 4 degrees C). Seawater at the same
temperature near the surface has a density of about 1.028. So,
the density only increases 1% in 7,000 ft.
As to how that pressure will affect the bouyancy of a “TEST
SUBSTANCE”; it all depends on what the test substance is. If you
are thinking about gemstones or other non-porous solids, the
answer is, very little especially when you consider that the test
substance will TEND to increase in density also.
You’ve really tweaked my interest in what you may be considering
doing at 7,000 ft. Why don’t you drop me a note