PELEUS AND THETIS
       Thetis was destined to bear a son mightier than his father. Zeus learned this secret from Prometheus and avoided mating with Thetis; she married instead a mortal named Peleus, who was hard pressed to catch his bride. For Thetis possessed the power of changing shape, and transformed herself into a variety of states (e.g., a bird, tree, tigress) in rapid succession, but eventually she was forced to succumb. Peleus and Thetis celebrated their marriage with great ceremony, and their son Achilles did indeed become mightier than his father.

ACIS, GALATEA, AND POLYPHEMUS
Galatea, another Nereid, was loved by the Cyclops Polyphemus, a son of Poseidon. Ovid's account (Metamorphoses 13. 750-897) presents a rendition of their story, playing upon the incongruity of the passion of the monstrous and boorish giant for the delicate nymph. Repelled by his attentions, she loved Acis, handsome son of Faunus and a sea-nymph, Symaethis, daughter of the river-god, Symaethus, in Sicily. Overcome by emotion, Polyphemus attempted to mend his savage ways; he combed his hair with a rake and cut his beard with a scythe.

Ovid's Galatea tells how the fierce Cyclops would sit on the cliff of a promontory jutting out to the sea, where he would lay down his staff (a huge pine-trunk the size of a ship's mast) and take up his pipe of a hundred reeds. Hiding below in the arms of her beloved Acis, Galatea would listen to his song. First he would extravagantly describe her magnificent beauty, then bitterly lament her adamant rejection of him and continue with an offer of many rustic gifts

POSEIDON AND AMPHITRITE
The third Nereid, Amphitrite, is important mainly as the wife of Poseidon; like her sister Thetis she proved a reluctant bride, but Poseidon finally was able to win her. As husband and wife they play roles very much like those enacted by Zeus and Hera; Poseidon has a weakness for women, and Amphitrite, with good cause, is angry and vengeful. They had a son, Triton, a merman, human above the waist, fish-shaped below. He is often depicted blowing a conch shell, a veritable trumpeter of the sea; he can change shape at will.

PROTEUS
The sea divinity Proteus, probably another of the older generation of gods, is often named as the attendant of Poseidon or even as his son. Like Nereus, he is an old man of the sea who can foretell the future; he can also change shape.  It is easy to see how the identities of Nereus, Proteus, and Triton could be merged.  Confusion among sea divinities and duplication of their characteristics are everywhere apparent.

THE APPEARANCE AND CHARACTER OF POSEIDON
Poseidon is similar in appearance to his brother Zeus, a majestic, bearded male, but he is generally more severe and rough; besides, he carries the trident, a three-pronged  fork resembling a fisherman's spear. By his very nature Poseidon is ferocious. He is called the supporter of the earth but the earth-shaker as well, and as a god of earthquakes he exhibits his violence by the rending of the land and the surge of the sea. By a mere stroke of his trident he may destroy and kill. His relentless anger against Odysseus for the blinding of Polyphemus provides a dominant theme in the Odyssey. The Homeric Hymn to Poseidon attempts to appease his anger.

The origins of Poseidon are much disputed. If his trident represents what was once a thunderbolt, then he was in early times a god of the sky. More  attractive is the theory that he was once a male spirit of fertility, a god of earth who sent up springs. This fits well with his association with horses and bulls (he either creates them or makes them appear) and explains the character of some of his affairs. He mated with Demeter in the form of a stallion; he pursued her while she was searching for her daughter, and her ruse of changing  into a mare to escape him was to no avail. Thus we have the union of the male  and female powers of the fertility of the earth.   It nevertheless should be remembered that standard epithets of the sea are "barren" and "unharvested"  as opposed to the fecundity of the land.

The important story of the contest between Poseidon and Athena for control of Athens and its surrounding territory, Attica, is represented in the sculpture of the west pediment of the Parthenon.

SCYLLA AND CHARYBDIS
      Poseidon made advances to Scylla, the daughter of Phorcys and Hecate. Amphitrite became jealous and threw magic herbs into Scylla's bathing place. Thus Scylla was transformed into a terrifying monster, encircled with a ring of dogs' heads; her home was a cave in the Straits of Messina between Sicily and Italy. With her was Charybdis, the daughter of Poseidon and Ge, a formidable and voracious ally whom Zeus had cast into the sea by his thunderbolt; three times a day she drew in mountains of water and spewed them out again.