If you look at a map of the globe, it's easy to see that there is really only one ocean.
While there is only one global ocean, the vast body of water that covers 71 percent of the Earth is geographically divided into distinct named regions. The boundaries between these regions have evolved over time for a variety of historical, cultural, geographical, and scientific reasons.
Historically, there are four named oceans: the Atlantic, Pacific, Indian, and Arctic. However, most countries—including the United States—now recognize the Southern (Antarctic) as the fifth ocean. The Pacific, Atlantic, and Indian are known as the three major oceans.
The Southern Ocean is the 'newest' named ocean. It is recognized by the U.S. Board on Geographic Names as the body of water extending from the coast of Antarctica to the line of latitude at 60 degrees South. The boundaries of this ocean were proposed to the International Hydrographic Organization in 2000. However, not all countries agree on the proposed boundaries, so this has yet to be ratified by members of the IHO. The U.S. is a member of the IHO, represented by the NOS Office of Coast Survey.