ocean water

There are four temperature scales that give us a relative understanding of the heat in the object or system we are measuring: Fahrenheit, Celsius, Kelvin, and (the less-common) Rankine. The Fahrenheit and Celsius scales are based on two fixed points, the Kelvin and Rankine scales are based on one.

http://www.onr.navy.mil/focus/ocean/water/temp1.htm

oceans

Combined, the four oceans cover seventy-one percent of the Earth's surface.Though generally described as several 'separate' oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean. This concept of a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography in is ninety-s.

Plate Tectonics

The ages of ocean crust and the thicknesses of ocean-floor sediments increase with distance from an ocean ridge. The theory of plate tectonics has done for geology what Charles Darwin"s theory of evolution did for biology.
http://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html