Rising out of the water above you is a massive humanoid figure shaped from the very liquid itself. The form shifts and changes, but the underlying shape remains the same — a colossal figure that vaguely resembles a humanoid, with swirling blue-green colors whirling within. Only the eyes, a pair of glowing yellow spots in the amorphous head, remain islands of stability.

Neptulon the Tidehunter reigns supreme in his domain, the deep ocean. Users of boats and other such water-crossing utilities risk his wrath; entering his domain without express permission is paramount to doom. He revels in taking those whom feel invulnerable, especially Therazane's rocky beaches and the flames of Ragnaros, when given the chance. He rules over all water, whether it be the sea, the ocean, river or lake. All water elementals worship him, as do all creatures that use water or the cold for their abilities. It is said that when an intelligent creature drowns, his or her soul will pass through his realm on the way to its end. It is supposed that he keeps those souls which amuse and interest him, but Neptulon only laughs at such suppositions.NOTE:  Neptulon will appear in Throne of the Tides in Cataclysm. Based off of beta, it seems as if you must defend Neptulon from waves of enemies.  According to the main quest chain in vash'jir, it seems the naga are trying to overthrow Neptulon and take over his kingdom; the water.
Neptulon could be the mysterious force directly responsible for transformations of the naga, the insidious influence behind Queen Azshara, the recent invasions of murlocs, and other underwater events, including the beached sea creatures at Darkshore and the presence of the Twilight Hammer at Blackfathom Deeps. It is known that the Old Gods were involved in the naga transformation, and Neptulon may have been a conduit for the change. However, given that the Naga are trying to overthrow the Elemental Lord, this casts doubt on this theory.