Hydrazoa $19.00 – $400.00 Hydra is a genus of small, fresh-water animals of the phylum Cnidaria and class Hydrozoa. They are native to the temperate and tropical regions.[2][3] Biologists are especially interested in Hydra because of their regenerative ability – they appear not to ageor die of old age. Select options This product has multiple variants. The options may be chosen on the product page