The planet is approximately 71% water and although the oceans of the earth are all connected (you can sail in a boat in every known “ocean” and “sea”) and truly one “World Ocean,” most often the world is divided into five major “oceans”.
Those five oceans, are the Indian, Pacific, Arctic, Atlantic, and, most recently, Southern.
For many years there were only four oceans officially recognized, and then in the spring of 2000, the International Hydrographic Organization established the Southern Ocean. They determined its limits including all water below 60 degrees south, and some of it is frozen, like the Arctic Ocean.
Oceans by size:
#1 Pacific (155,557,000 sq km)
#2 Atlantic (76,762,000 sq km)
#3 Indian (68,556,000 sq km)
#4 Southern (20,327,000 sq km)
#5 Arctic (14,056,000 sq km)
Greatest depths in the each ocean:
* Mariana Trench, in the Pacific 35,827 ft
* Puerto Rico Trench, in the Atlantic 30,246 ft
* Java Trench, in the Indian 24,460 ft
* Arctic Basin, in the Arctic 18,456 ft
* Southern Ocean (greatest depth is in dispute)