Hydra are tiny freshwater predators of the Phylum Cnidaria. They can be found in unpolluted freshwater in temperate and tropical regions. Hydra appear to be biologically immortal, they do not age. They are also capable of asexual reproduction. If conditions are right, a bud grows in the body wall, developing into a miniature of the adult and eventually breaking away. Sexual reproduction via free-swimming gametes occurs when conditions are less ideal. The Hydra feeds on small aquatic invertebrates. First they extend their body, then the tentacles - which can stretch to 5 times the body length - and wait for prey to swim into their clutches. The prey is then stung, subdued and drawn back to the mouth aperture to be consumed.