The Sea
The sea, the world ocean or simply the ocean is the connected
body of salty water that covers over 70% of Earth's surface
(361,132,000 square kilometers (139,434,000 sq mi), with a total
volume of roughly 1,332,000,000 cubic kilometers (320,000,000 cu
mi)). It moderates Earth's climate and has important roles in the
water cycle, carbon cycle, and nitrogen cycle. It has been
travelled and explored since ancient times, while the scientific
study of the sea—oceanography—dates broadly from the voyages
of Captain James Cook to explore the Pacific Ocean between 1768
and 1779. The word sea is also used to denote smaller, partly
landlocked sections of the ocean and certain large, entirely
landlocked, saltwater lakes, such as the Caspian Sea and the
Dead Sea.