Undine

Aeetes of Colchis, in The Hidden Powers, names the undines as the elementals of water who rule the earth's waters, and says a successful Summoning of Elementals may bind these solitary spirits to a mage's service if his power is great enough and the task just.

On our plane an undine looks like a seven-foot, loosely human shape of water held together, draped in algae, seaweed and all sorts of water plants. It drips constantly and brings with it an overwhelming, rank smell, so it is said to be poor company. Unlike earth gnomes, undines can leave their element for a while: they cannot work in hard frost or very dry air, but they can walk on dry land for short spells. They can also scatter into a broad bank of fog at will, drifting freely before taking shape again, and in a body of water one can swell to as much as ten times its size, a towering and fearsome mass of water, though only for a few moments.

Undines are loners both at home and in our world. Here they sometimes dwell in lakes, rivers and other waters and guard them jealously, so damming or even bridging a river may displease the local elemental, and a wise builder tries to appease it first. Some undines protect the gentle nymphs called Nyads, and harming one may bring its guardian's anger. They are not close-knit like the gnomes, however, so offending one undine hardly matters to another. Apart from that they pay little heed to other creatures, though they watch their own territory closely.

An undine can cast any water-related spell up to fifth level, one per level each day.