The recent increase in human life expectancy is accompanied with a more frequent occurrence of age-related diseases such as neurodegenerative diseases and cancers. An unprecedented effort has been dedicated to develop animal model systems to decipher the aging mechanisms, and the genetic study of short-lived animals, namely Drosophila and Caenorhabditis, brought important breakthroughs. Here we highlight the interest of additional model systems like the cnidarian Hydra polyp. Hydra provides a model where all tissues continuously renew from large stocks of proliferative adult stem cells, where amputation leads to regeneration with perfect replacement of any lost body structure and where signs of aging remain limited over the years. Aging is easily inducible in some Hydra species, providing a paradigm for deciphering the mechanisms that promote resistance to aging. A dynamic autophagic flux, a sustained proteostasis, the G2 pausing of stem cells and an efficient DNA-damage repair might play an essential role.