When Poseidon was born he was swallowed by his father Cronus along with his brothers and sisters, Hades, Hestia, Demeter, and Hera. Zeus though was never swallowed and freed his brothers and sisters from their father. For ten years there was a war and the six siblings fought in it till the end. 

They battled their father, aunts, and uncles- the mighty Titans. The war was awful, but Posiden did his part and never gave up, he wasn’t a coward. Now and then the war would lull for even immortals needed to rest and recuperate. During these times Posiden would visit Pontus, the ancient god of all the waters, the partner to his grandmother, Gaia, the mother of earth, and his grandfather Uranus, the father of heaven. When Poseidon swam in Pontus waters he felt happy despite all the bad things he was experiencing and the terrible war that raged on the land above the water.

Poseidon found joy in diving with whales, he found a beauteous rhythm in the undulating wake of eels, and he found humor in the scuttling of crabs at the bottom of the ocean, but best of all Poseidon made a friend with the oldest son of Pontus and Gaia. 

His friend’s name was Nereus, and he loved the watery depths as much as Poseidon did. Together they would plunge down below to where the corals and sponges lived. They rode on the backs of turtles and flapped their arms like the stingrays they swam with. 

Sadly though Poseidon would have to go back to war. That was until the hundred-handed sons of Gaia joined in on the battle. They were strong and completely changed the battle. The Cyclopes fought along with the gods too and they brought gifts to the three brothers. The Cyclopes gifted Zeus the thunderbolt, Hades the helmet of invisibility, and Poseidon the trident. 

Poseidon loved his trident. He could strike the ground with it and the earth would shake and the seas and rivers would overflow with water. With the help of these gifts and their alliance with the hundred handed men and the Cyclopes, they won the war. Zeus appointed Poseidon ruler of the seas. Poseidon knew that his brother gave him the seas because he felt they were an inferior realm to rule, but nothing could have pleased Poseidon more. 

Poseidon swam the seas in search of those who might need his help. When he wasn’t patrolling, he let himself be absorbed in the watery mysteries of the sea. That’s when he discovered the finest mystery ever. She was the granddaughter of Pontus and Gaia, and the daughter of the lordly sea god Phorcys and the lovely cheeked sea goddess Ceto. That heritage made her the perfect wife in Poseidon’s eyes. She was one of three sisters, called the Gorgons. The other two sisters were immortal, like the gods, but Medusa, as she was called, was mortal. 

Poseidon found her mortality alluring. He thought of her as vulnerable and how amazing it was to him to know someone vulnerable. Medusa made him feel safe. You see her hair was made of snakes that could bite and that made for good protection. She had wings that grew from her back that were strong that could carry him far away from any attacker. She had scales that were stronger than any armor and the most assuring thing about her was her power. Anyone who looked at her in the eyes would turn to stone, and so Poseidon felt safe in her arms. They revealed together in his sea kingdom happy, but their love was not meant to be so they eventually grew apart from each other.

(Source: Treasury of Greek Mythology by Donna Jo Napoli)