Hydra is the largest constellation of all, but also one of the least known since so many of its stars are
fourth- and fifth-magnitude or fainter.
Also, while Hydra contains a number of Messier objects and other deep sky objects, none could be considered ‘exceptional’.
There are, however, several very fine binaries and some notable variables. And--like Eridanus--just being able to follow its stars across a great swath of sky can be considered a fine accomplishment.
The Hydra makes its first appearance late in Winter, and over the next few months slowly slithers across the skies earlier and earlier.
The most logical way to begin investigating Hydra is to start at the Hydra's Head, the tight asterism just south of Cancer.
Alternatively, you can begin at the Hydra's heart, alpha Hydrae. This bright star forms a triangle with Procyon and Regulus: Alphard.