There really is only one ocean, consisting of five component basins that are called the Atlantic, the Pacific, the Indian, the Arctic, and the Southern. Each of these five, while generally referred to as oceans in and of themselves, are really and truly a part of a single, massive body of water, one ocean which defines the very face of planet Earth.
The ocean covers roughly 71% of Earth's surface, some 360 million square kilometres. The ocean represents 97% of Earth's total water content. On top of all that, the ocean contains upward of 99% of the world's biosphere. In fact, with roughly 50% of the world's population living within 100 kilometres of the coastline and with most of the remainder living close enough to lakes, rivers, or swamps, all of which ultimately lead to the ocean, virtually every single person on the planet has the opportunity to influence the general health and nature of the world ocean.