Neptune is identified with Poseidon, the Greek god of the sea.

Mythology

IIn Roman religion Neptune was a god of water, not a god of the sea, until he became identified with Poseidon, the Greek god of the sea. Neptune may have originated from an Etruscan deity and his festival was one of the earliest in Roman religious observances. The symbol of Neptune's power was a three-pointed spear, or trident. He used his trident to shatter rocks, to cause havoc on the shores, or to summon storms or to subdue them. The creator of the horse and patron of horse races, his own horses had golden manes and brazen hoofs and drew his chariot over the sea, which became smooth before him while the monsters of the deep oceans cavorted about on either side of his path.