Most of Earth’s water (97 percent) is in the ocean. Seawater has unique properties. It is salty, its freezing point is slightly lower than that of fresh water, its density is slightly higher, its electrical conductivity is much higher, and it is slightly basic. Balance of pH is vital for the health of marine ecosystems and important in controlling the rate at which the ocean will absorb and buffer changes in atmospheric carbon dioxide.

Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.