There's a type of jellyfish that's immortal - Apparently.
The Turritopsis dohrnii, also known as the "immortal jellyfish," is a species of jellyfish that can transform its body into a younger state through a process called transdifferentiation. This means it can essentially revert back to its polyp stage, which is the juvenile form of a jellyfish, and then grow back into an adult again. This process can be repeated indefinitely, making the Turritopsis dohrnii theoretically immortal. This process was first discovered in the 1990s and has been studied extensively in laboratories.