The Poseidon Myths
In the Poseidon myths we learn that he was the god of the sea and of horses, brother of Zeus and Hades, and a bad-tempered, horny devil just like them. Poseidon in Greek mythology is sometimes depicted in true merman form with a fish's tail from the waist down. His symbol is the trident, a three-pointed spear like a pitchfork. Later, the early Christians gave this symbol to the devil. Waving his trident Poseidon could call up storms out of the ocean, or he could thrust it into the ground to cause earthquakes. According to the Poseidon myths he had a palace under the sea with an enormous stable filled with white horses who pulled his chariot over the ocean. "White horses" is an old expression referring to the white part of a breaking wave.
His wife was Amphitrite, a sea nymph and daughter of Nereus and Doris. Before they were married, when Poseidon was courting Amphitrite, she had heard about his bad reputation and hid in the Atlantic Ocean. According to this myth Poseidon sent numerous sea creatures to find her, but they all came back empty handed. Finally, he sent his servant Delphin (a dolphin) out to find Amphitrite. Delphin located her and talked her into coming back with him. As a reward Poseidon turned Delphin into the constellation dolphin, which is still called by that name.
Amphitrite had been a major goddess in her own right. Her name means "the third that surrounds". To the Greeks, the sky and land were the first and second things created, the sea was the third. And the sea naturally surrounds the land.
Amphitrite was jealous of Poseidon's lovers and once turned one of them into a sea monster. She was called Scylla, a beautiful sea nymph. Amphitrite threw magical herbs into her bath and she was transformed into a horrible monster with six mouths and twelve feet. After this, she lived in a cave above a narrow strait, and whenever a ship passed she would use her long necks to take sailors from the deck and eat them. It was in this way that she got six of Odysseus' men when his ship came too near her home.
Scylla's story has another version which substitutes Circe for Amphitrite, but the outcome is the same.
In the Poseidon myths, he and Amphitrite had a son named Triton, who had the body of a man and the tail of a fish (do you see a pattern?). He lived with them in their golden palace under the sea. He rode the waves on horses or sea monsters, and blew on a twisted conch shell. He also appears in multiple forms, like clones, that are associated with other sea gods. Triton was also a sea-elder, he knew all things past, present and future. Triton helped out Jason (of the Argonauts) by carrying his ship from Like Tritonis to the Mediterranean.
In one of the other Poseidon myths, he fought battles with his niece Athena in order to gain control of her kingdoms. Athena was the goddess of war and gave him a good fight every time. Zeus and the other gods were often called upon to interfere. Later, Poseidon fought with other gods: Zeus himself, Hera, Dionysus, Helius, etc. Poseidon destroyed buildings, flooded some lands and brought a bad drought to others. These Poseidon myths are really history transformed into mythology. Actual events were about one religious group trying to get a hand over another.