Today is St. Patrick's Day, which celebrates St. Patrick, patron saint or Ireland who, among other things, supposedly drove all the snakes from the land.
Unfortunately, St. Patrick missed the biggest snake of all: one that spans over 100 degrees of sky.
Hyrda the water snake was the mythological snake Corvus the crow brought back to Apollo instead of a cup of water (see also: constellations). Enraged, Apollo flung the snake (as well as the bird and empty cup) into the sky. To find Hydra, look below Cancer for a circle of stars that represent the snake's head. From there, go East, snaking (sorry) through the sky to Alphard, alpha star and heart of the snake, before continuing until the serpent's tail, which lies just West of Libra.