Hydra & Hydrus
The Water Serpent and The Little Water Serpent
Hydra and Hydrus are water snakes: the Greater and Lesser. The Greater Water Snake Hydra is a mystical beast that had the ability to regrow a severed head. Hydrus is a relatively new constellation invented by a French Astronomer -Nicolas Louis de Lacaille.
Out of the thousands of other mythical animals they could have chosen for the 'new' stars of the Southern Skies they chose to repeat themes that were already there. Why couldn't have they chosen a Griffin, Tiger, or Zebra? Nope, they had to stay in their comfort zone and went for the duality-yin yang balance theme: two lions, two water snakes, two triangles, two crowns, two bears, two centaurs, mostly just two 'similar whatevers.'
Note, both Serpent Icons face 'Sinister' since snakes are considered the master species of 'Sinister Behavior.'
The flag of Hydra the Lesser Sea Serpent, also called a water snake, spans on the pole in stark contrast to the larger equatorial serpent. But it effectively counters the Great Sea Serpent by swimming into the Celestial South Polar 80s, giving it a black stripe in its field and Navy Blue longitudinal band.