Long before man had the experience of long distance exploration with which to build a sense that the salted water surrounding his land mass had a beginning and an end, the spiritual belief that 'ocean' encompassed heavens and 'ocean' flowed in the deep. Many ancient forms of mythology speak of it. It is even noted in the first book of The Old Testament.
Over millions of years, ancient oceans have transfigured into the modern oceans we know today due to continental drift. Landlocked bodies of salt water such as the Aral Sea (which has now recently disappeared due to global warming) have been separated from the body of the world's oceans due to continental drift. Bodies of water such as (most) seas, gulfs, and bays edge and curve into the world's oceans as they fill out 71% of the earth's surface between the continents.
The oceans' waters sit on volcanic crust. The life of an ocean's floor is mainly coral beds. The coral beds are in a desperately depleted state at the moment due to global warming. It is a scientific consensus that there will be no good place for coral to grow by 2052 unless immediate action is taken to stop CO2 pollution. This is a major affront on the viability of the world's oceanic survival. Fish stocks are decreasing; extinctions are 1000 times greater in and out of the oceans than what they naturally should be; the acidity of the oceans is increasing every day as 1/3 of the world's CO2 emissions fall back into the oceans. This is a major threat to the world's oceans.
Geographically mapped, the world's oceans are divided into the Atlantic, Pacific, Indian, Arctic, and South - which is generally considered to be the most southern portions of the Atlantic, Pacific, and Indian Oceans. They are separated into zones and regions depending on factors such as depth. The deepest known point in the world's oceans is the Marianas Trench which was explored by challenger 11 in 1951.
The northern portions of the world's oceans experience the most dramatic tidal patterns. Tides are an average 12-hour shifting of the waters in unison with the gentle pull of the moon. Tides may vary as much as 25 feet over a 12-hour period.
The power and majesty of the world's oceans has long captivated men's adoration and respect. Many weathered seafarers have lost their lives on those oceans; a few of them acquaintances of mine. I've been a fisherman for almost ten years and although I've long ago stopped making a living from the ocean, I still pine longingly whenever I'm in sight of it. It gets in your blood, man against the elements, I guess. It is the strongest closeness with nature I've ever experienced and my love for the ocean is rooted to the depths of my soul.