维基百科Mariana Trench(马里亚纳海沟)
At the bottom of the trench thewater columnabove exerts a pressure of 1,086 bars (15,750 psi), over 1000 times thestandard atmospheric pressureat sea level. At this pressure the density of water is increased by 4.96%, making 95 litres of water under the pressure of the Challenger Deep contain the same mass as 100 litres at the surface.大意是:在10km 深的海底里,压力超过1000倍标准大气压,水的密度会增加4.96%,所以这里95升的水的质量等同在水面的100升水的质量。
这个答案只是尝试从另一个角度去思考这个问题。