Hydrus is a small constellation in the southern hemisphere, created by the Dutch astronomer Petrus Plancius from the observations of explorers Pieter Dirkszoon Keyser and Frederick de Houtman in the 16th century. Its name means "male water snake" in Latin. It is also often referred to as the Lesser Snake or the Little Water Snake, the name under which it appeared in Johann Bayer's Uranometria
in 1603. (The much larger female water snake is represented by the constellation Hydra
Hydrus represents the sea snakes Dutch navigators saw on their journeys. To make a greater distinction between the genders, the French astronomer Nicolas Louis de Lacaille named the constellation l’Hydre Mâle on his map of the southern skies in the 18th century.
The constellation Hydrus occupies an area of 243 square degrees and contains one star with known planets. It can be seen at latitudes between +8° and -90° and is best visible at 9 p.m. during the month of November. Hydrus is located right between the Magellanic Clouds.
The constellation does not have any named stars and contains only very faint deep sky objects. The brightest stars are only of third magnitude and form a triangle in the sky. The brightest star is 
beta Hydri, the nearest bright star to the southern celestial pole. It is a yellow-orange star 24.4 light-years distant, more evolved than our Sun and the closest known subgiant to the Sun. It is often studied as a source of insight into what might happen to the Sun over the next couple of billion years.
alpha Hydri, an F-class dwarf approximately 810 million years old, lies about 71 light-years from Earth.
gamma Hydri, the third brightest star in the constellation, is a luminous red giant 214 light-years distant.
The most interesting deep sky object observed in Hydrus, IC 1717, is now curiously missing. It was observed and documented by the Danish astronomer John Louis Emil Dreyer, who described it as "excessively faint" and "excessively small," but nothing can be seen at the coordinates he gave for the object, near 
eta-2 Hydri, a yellow giant star with a planetary system. The only logical explanation scientists have offered for the missing object, other than an error in observation, which would have been highly uncharacteristic for Dreyer, is that the coordinates may have been the site of a destroyed planet and what Dreyer had seen was the just the trail of the planet’s final orbit.
Hydrus also contains a notable small, narrow, relatively bright nebula, NGC 1511, and a small elliptical galaxy, NGC 1473.
Hydrus belongs to the Johann Bayer family of constellations, along with Dorado
Constellations directly bordering Hydrus are Dorado