Oceanus or Okeanos refers to the ocean, which the Greeks and Romans regarded as a river circling the world. In Greek mythology this world-ocean was personified as a Titan, a son of Uranus and Gaia. In ancient Greek reliefs this Titan is often depicted as having the upper body of a muscular man with a long beard and horns, and the lower torso of a serpent. (Compare Typhon.)
Oceanus' consort is his sister Tethys, and from their union came the ocean nymphs, also known as the three-thousand Oceanids, and all the rivers of the world.
Some scholars believe he originally represented all bodies of salt water, including the Mediterranean Sea and the Atlantic Ocean, the two largest bodies the ancient Greeks knew of. However, as geography became more accurate, Oceanus came to represent the stranger, more unknown waters of the Atlantic Ocean (also called the Ocean Sea) while Poseidon ruled over the Mediterranean.
In most variations of the war between the Titans and the Olympians ("Titanomachy"), Oceanus, along with Prometheus, and Themis, did not take the side of their fellow Titans against the Olympians, but instead withdrew from the conflict. In most variations of this myth Oceanus also did not side with Cronus in his revolt against Uranus.
In Iliad the rich iconography of Achilles' shield that Hephaestus made, is enclosed, as the world itself is, by Okeanos:
"Then, running round the shield-rim, triple-ply,
he pictured all the might of the Ocean stream."
Oceanos was the name of a Greek cruise ship that sank off of the coast of South Africa in 1991. No lives were lost, but the Captain and crew left before many of the passengers.
Oceans (from Ὠκεανός Okeanos in Greek, the ancient Greeks noticing the strong current that flowed off Gibraltar and assuming it was a great river) cover almost three quarters (71%) of the surface of the Earth, and nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep.
The original concept of "ocean" goes back to notions of Mesopotamian and Indo-European mythology, imagining the world to be encircled by a great river, Okeanos, "Ωκεανός" in Greek, Samudra in Hindu mythology (compare also Jörmungandr, the sea serpent living in that outer ocean in Norse mythology).
The world was imagined to be enclosed by a celestial ocean above the heavens, and an ocean of the underworld below (compare Rasā, Varuna).
Ocean (from Okeanos, Greek for river, the ancient Greeks noticed that a strong current flowed off of Gibraltar, and assumed it was a great river; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth, and nearly half of the world's marine waters are over 3000 m deep.
Some geographers and some governments but not the US, recognize the IHO as defining official water body names and boundaries.