That only seems to occur in a small portion of a specific jellyfish family though: "Another unusual species, T. nutricula, falsely reported as Turritopsis dohrnii, might be effectively immortal because of its ability under certain circumstances in the laboratory to transform from medusa back to the polyp stage, thereby escaping the death that typically awaits medusae post-reproduction if they have not otherwise been eaten by some other ocean organism .[44] So far this transdifferentian of life form has been observed only in the laboratory and it is not known if it actually occurs in wild Turritopsis populations."

I'm with you, Capiton

Ooo, he's a smart one.