Shapeshifting Jellyfish!
The Mangrove Cassiopea (Cassiopea xamachana) passes successively from a state of larvae to a polyp and, upon reaching a certain size, is released as a free-swimming form. From then on, it keeps growing until it naturally starts the whole process again.
“Upside-down Jellyfish” are rather small but can grow to a diameter of 25cm (10 in).