Like his younger siblings, Oceanus was born to Gaea and Ouranos, the respective personifications of the earth and sky. The Titans were the eldest of the three races born to Gaea the Earth and Ouranos the Sky, before the Hekatonkheires (Cottus, Gyges, and Briares) and the Elder Cyclopes (Arges, Brontes, and Steropes), while Oceanus was the eldest Titan of all. He would spend most of his time in the company of Pontus, the primordial god of the Sea, whom he affectionately referred to as "Uncle Pontus."
While Ouranos detested all of his children, he detested the Elder Cyclopes and Hekatonkheires so much (mainly for their ugliness) that he imprisoned them in the terrifying abyss of Tartarus, which was itself deep within the Earth. Enraged, Gaea told her remaining twelve children (including Oceanus), the Titans, to take the mighty Scythe that she had forged, and avenge their brothers by overthrowing and killing their arrogant and sadistic father. Being immortal, Oceanus initially did not even understand what "killing" meant, but the concept was quickly explained to him by Themis, his most intelligent sister. However, while Oceanus detested his father, he was ambivalent at the prospect of murdering him, and did not step up to take the Scythe. Even after his youngest brother Kronos did, Oceanus claimed that he had important business to attend to under the sea, and refused to help in the murder (along with his sisters Theia, Tethys, Themis, Phoebe, Mnemosyne, and Rhea). Thus, Oceanus was the only male Titan who was not involved in his father's murder. After committing his evil deed, Kronos hurled all of the remaining pieces of Ouranos into the sea as a gesture of loathing against Oceanus for not helping slay their father. Much later, these particles would mix with the ocean spray to form Aphrodite.
Titan Lord of the Seas
After Kronos claimed his supremacy as the Titan King of Mount Orthys, and ushered in the "Golden Age", Oceanus became the Titan Lord of the Seas, and was nicknamed "Father of the Waters" (since Pontus took to spending all of his time in deep slumber). Oceanus would also rule over the huge body of water that encircled the flat earth. As a result, the world's largest bodies of water began to be called "oceans", named after the eldest Titan that ruled them. Oceanus would also frequently approach his wise and clairvoyant brother Koios with questions about the future.
In time, Oceanus attracted the attention of his sister Tethys (the Titaness of the Sea), who often annoyed her other siblings with her obsession over water. After marrying Tethys, Oceanus fathered 3,000 ocean nymphs (called the Oceanids), and 3,000 river gods (called the Potamoi). As a result, Oceanus and Tethys had more children than any of the other Elder Titans. Shortly after the birth of his many children, Oceanus no longer visited Kronos on Mount Orthys, not even during the latter's weekly Sunday dinners. While he claimed to be too busy, Kronos knew that the actual reason was Oceanus' secret fear of his brother's might and infamous temper.
Zeus Rescues His Siblings
However, years later, after Kronos hired a young Titan by the name of Zeus (actually a god in disguise), Oceanus was very entertained by the latter's excellent singing, dancing, and "Satyr jokes", and took to visiting Kronos on Mount Orthys more often. Shortly thereafter, Zeus encouraged Oceanus to participate in the newly established Titanic drinking contests. As the Titan King of Mount Othrys, Kronos would always win, since he could not let his siblings or nephews overcome him in anything.
One evening, when Oceanus was dining with his brothers and nephews, Zeus prepared nectar mixed with sleeping potion for Oceanus, and a powerful emetic for Kronos. As before, Zeus entertained them all with his great singing, dancing, and jokes. Near the end of the Titanic banquet, Zeus encouraged all of the Titans to have yet another drinking contest, and handed out the prepared goblets. As before, Kronos won the contest, but the emetic caused him to disgorge all his swallowed children, while Oceanus was temporarily knocked out by the sleeping potion, and could not stop them from escaping.
Shortly thereafter, all six of Kronos' children quickly declared war against their father, as well as the other Titans. Shortly before the Titanomachy began, Oceanus' sister Rhea personally visited him and Tethys, and convinced them to remain neutral in the upcoming conflict.
The Titans initially had the upper hand in their battles with the gods, since they were well-armed, and much more experienced warriors. However, the gods quickly became skilled warriors as well, and with the help of their new extremely powerful weapons (Zeus's Master Bolt,Poseidon's Trident, and Hades's Helm of Darkness), as well as the aid of the Elder Cyclopes and Hekatonkheires, the gods finally prevailed. During the final battle, Zeus used his Master Bolt to shear off the top of Mount Othrys, and hurl Kronos from his Black Throne. In the aftermath of the battle, Zeus sliced his father Kronos into a thousand pieces with his own Scythe, and hurled his remains into Tartarus, along with Hyperion, Iapetus, Krios, and Koios. Since he was neutral, Oceanus was the only Elder Titan whom Zeus, Poseidon, and Hades did not imprison in Tartarus after the war.
When Zeus, Poseidon, and Hades (the Big Three Olympians) divided the world between themselves, Poseidon seized the seas and oceans. As a result, Oceanus willingly gave up his throne as Lord of the Seas to Poseidon, and peacefully retreated to the deeper sea, along with his wife Tethys.
Oceanus' Olympian niece Hera was the most beautiful Olympian goddess of all, and was desired by many gods and Titans. However, Hera also had a fierce and infamous temper, and would arrogantly rebuke anyone who ever tried to woo her. As a result, her mother Rhea decided to send Hera to Oceanus and Tethys, where she might learn to tame her temper and act mature. Hera spent a number of happy years with them, away from Mount Olympus. After seeing how stable and loving Oceanus and Tethys' marriage was (more so than most other marriages between immortals), Hera decided to strive for a similar one for herself. Overall though, while Oceanus did help Hera tame her infamous temper by the time of her return, many gods were still wary of openly flirting with her, since she was determined to find a perfect husband for herself.
While Oceanus was neutral in the first war, his brother Kronos finally convinced him to fight against the Olympians, more specifically his nephew Poseidon. Oceanus enlists Phorcys, Aigaios as well as many ancient monsters (gigantic squids, Sea serpents, Leviathans, and Keto) against Poseidon, and they battle constantly, leaving Poseidon somewhat weakened. Oceanus and his forces attack Poseidon underwater, making his palace endangered and also making him unable to aid the Olympians in their fight against the monster, Typhon. When Percy enters the battle, Oceanus advances and challenges Poseidon himself to a duel. As Percy is leaving, Poseidon engages Oceanus in an enormous clash which causes extremely violent tsunamis and wave, and lights can be seen flashing as the two warriors do battle. When Poseidon chose to aid the Olympians, Oceanus probably did serious damage to Poseidon's palace. After Kronos was defeated, he retreated back into the depths.
Oceanus was shown to not be as arrogant or cruel as his brothers, being the only Elder Titan to not help in the murder of Ouranos. In Percy Jackson's Greek Gods it was shown that he was a bit slower than his siblings, not initially understanding what Gaea meant by kill (though as they were immortal it was understandable). Unlike most immortals Oceanus actually had a happy marriage with his wife and was faithful to her.
In The Last Olympian, Oceanus was described by Percy as a huge merman, much larger than the rest, with the upper body of a tall and muscular man, with a long green beard and hair, along with the horns of a bull. Oceanus appeared to be riding a chariot pulled by huge crawfish with a serpent as a weapon. As seen in Percy Jackson's Greek Gods however, Oceanus can transform his lower body into legs while on land.
While not quite as strong as Kronos or Hyperion, Oceanus is still extremely powerful as the eldest Titan. While the true extent of his power is never seen, he seemingly rivals that of his nephew Poseidon, which allowed him to wage an intense underwater war against the latter.
- Hydrokinesis: Being the Father of Waters and Titan Lord of the Seas, Oceanus has absolute control over water, which rivals that of his nephew Poseidon. Hence, Oceanus is the only one who can successfully fight the latter at sea.
- Tsunamis and Tidal Waves: Oceanus can unleash gigantic tsunamis and tidal waves, as seen during his battles with Poseidon in The Last Olympian.
- Hydrogenesis: Oceanus can create water from his own power, generating it out of nothing.
- Water Propulsion: He can control the water around him to propel himself through water at incredible speeds.
- Water Solidification: He can harden water into an almost solid shape, and can use this power to walk on water, by increasing the surface tension of the water to the point where it is solid enough for him and other objects to stand on. He can also create extremely durable water shields and huge solid constructs that obey his will.
- Water Blasts: He can unleash water blasts powerful enough to easily send gods or Titans flying.
- Floods and Droughts: He can bring about both floods and droughts.
- Water Pressure Immunity: He can withstand any amount of water pressure.
- Water Creation: He can generate water from his body and create water springs.
- Water Transportation: He can use sea waves as a form of high-speed transportation.
- Underwater Breathing: He can naturally breathe underwater.
- Heat Resistance: Oceanus has an extreme resistance to heat and burns, slightly inferior only to that of his grand nephew Hephaestus.
- Atmokinesis: Being the Father of Waters and Titan Lord of the Seas, Oceanus has control over the weather, which rivals that of his nephew Poseidon.
- Storm Generation: Oceanus can bring forth hurricanes and storms.
- Aquatic Monster Lordship: Oceanus has absolute control over many ancient and powerful monsters, such as gigantic squids, Sea serpents, Leviathans, and Keto. In The Last Olympian, Poseidon mentions that these sea monsters are so ancient, that even he had forgotten about them. Oceanus managed to gather them all to attack Poseidon on many fronts, in a constant war that lasted for more than a year.
- Titanic Divine Form: As Kronos's elder brother, it is possible that Oceanus also had the ability to incinerate any being less than a god/Titan only by being present.
- Tongue of the Old Times fluency: According to Tyson in The Battle of the Labyrinth, this is the ancient language that Gaea spoke to the Titans, Elder Cyclops and Hekatonkheires before the birth of the Olympian gods. Hence, Oceanus understands and speaks it perfectly.
- Leadership Abilities: Oceanus led the aquatic portion of the Titan attack against the Olympians. Oceanus' year long siege against Poseidon led to a stalemate between the two with Oceanus not only leading ancient sea gods and spirits but also summoning ancient monsters so old that Poseidon had forgotten about them. Oceanus' purpose being to isolate Poseidon from the other Olympians and keep him from aiding in the fight against Typhon.
- Titanic Energy: Like all Titans, Oceanus can blast things hundreds of feet away from him with a yell or wave of the hand.
- Oceanus only ever appears in person in Percy Jackson's Greek Gods, as only a holographic image of him is seen in The Last Olympian.
- Oceanus is the eldest Titan son of Gaea and Ouranus, and thus, Kronos' eldest brother.
- Out of all of the Eldest Titans, Oceanus and Tethys had the most children.
- Oceanus was the only one of Kronos' brothers who was not involved in the murder of Ouranus, or the First Titanomachy. As such, he is the only male Elder Titan who never gets thrown into Tartarus.
- After his nephew Poseidon takes over as Lord of the Oceans and Seas, Oceanus moves into deeper waters.
- The word "ocean" comes from his name, as he is the Father of the Waters.
- According to Percy Jackson's Greek Gods, Oceanus and Tethys, were one of the most loving and loyal married pairs among immortals.
- In Percy Jackson's Greek Gods, after the Titanomachy, Oceanus and Tethys raised Hera for years, and helped her tame her infamous temper.
- In The House of Hades Hyperion declared that Iapetus was the least cruel of the Elder Titans. It is unknown if this statement included Oceanus, who was not a part of murdering their father nor was known for any particular cruelties.