Water is the most powerful force in the universe. It is capable of crumbling a mountain or digging great canyons. And the water element is no different. Surprisingly, it is the most destructive of the elementals.
Easily the most useful level 3 summoning spell, as even a small stack of water elementals can be a great support, casting Quicksand, Slow and Weakness on your enemies and then casting Ice Bolt when that's done or when you've beefed up the stack enough that the spell will do significant damage.