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Hydra | Description & Mythology | Britannica
Hydra (genus) - Wikipedia
Hydra – Mythopedia
Hydra Greece – Complete Island Guide | Discover Greece
Hydra | Freshwater, Cnidaria, Polyp | Britannica
Hydra (Lernaean Hydra) - Serpent in Greek Mythology
What is a hydra? - Discover Wildlife
Lernaean Hydra - Wikipedia
Hydra – Biology, Classification, Characteristics, and Reproduction
How Tiny, ‘Immortal’ Hydras Regrow Their Lost Heads