To withstand the pressure over 14,000 feet down, the submersible Alvin's hull is this metal, about 2 inches thick
[DOC] [TLE] Full text of "Panel reports of the Commission on Marine Science ... [PAR] For example, magnesium metal ex- tracted from sea water accounts for over 90 
per ...... are known to exist on the continental rises at depths from 6,000 to 14,000 
feet.