Michiru- Ocean King (Queen in this case).
Mythology: Neptune is the Roman name for Poseidon, the Greek god of the sea. It is appropriate for Michiru to be the Senshi that has control over the oceans for this reason.
Neptune represents mystery, illusion, imagination, and the unexplainable. Neptune is the planet of bewitchment, idealism, spirituality, and the subconscious world. The down side to Neptune is that it also stands for deception, fraud, confusion, and treachery. However, Michiru is nothing like this.
Neptune brings people to be more academic, spiritualistic, and sometimes artistic, which kind of explains why Michiru plays the violin.
Neptune also represents perfection, the spiritual quest, and the search for the Impossible Dream.
Poseidon's connections to Michiru, are that the oceans are their province and He always carried a three pronged spear named the trident, which is on the back of Michiru's mirror. Poseidon is also described as having sea-blue hair, not too different from Michiru.
One of the islands that Poseidon raised out of the sea was Delos. It was so newly created that it was still floating about on the water. The little island was barren. Nothing grew on it yet except a single palm tree. In its shade, Artemis (ahem) was born.

Attacks:
Deep Submerge
Submarine Reflection: Aqua Mirror Reflector
Birthday: March 6