There are pictures of the Hydra on vases and bronze plates dating back as far as the 7th century BC. Hercules (who is called “Heracles” in Greek mythology) kills the Hydra as one of his labors. The Hydra lived in the lake of Lerna in the Argolis. The lake itself is older even than the Mycenaean city of Argos.

The Phylum Coelenterata consists of marine organisms that have a body that is radially symmetrical and a mouth that has sensory tentacles that help in capturing prey easily. Other animals belonging to the Phylum Coelenterata are hydra, comb jellies, true jellies, sea pens, coral animals, sea anemones and more.

Hydras belong to the phylum Coelenterata (also called Cnidaria), which includes corals, sea anemones, and jellyfish. Coelenterates are primarily marine animals, but hydras are found in freshwater ponds, lakes, and streams.

This hydra grows heads out of its other heads, and to kill it, you need to cut off the shortest head branches, lest it regrow that entire section twice (which it does any time you cut off a head anywhere).

The Hydra is an immortal, many-headed snake who haunted the swamps around Lake Lerna in ancient Greece. Although the monster claimed hundreds of victims, it is most famous for its battle with the hero Heracles.

The weakness of the Hydra was that only one of its heads was immortal. The details of the struggle are explicit in the Bibliotheca (2.5. 2): realizing that he could not defeat the Hydra in this way, Heracles called on his nephew Iolaus for help.

No gills, no heart, no brain, no eyes – of course, it would be hard to pack all those organs into a creature a few millimeters long, and hydra certainly seem to do well enough without them.