Immortal fish

Jellyfish are the oldest multi -organ animal and have existed for over 500 million years ! They have no brain , no heart and no bones. Their body consist of 98 % water and so they evaporate in the sun .
A species of jellyfish has been discovered which is biologically immortal. It achieves this by aging backward after maturity , going through reverse-puberty so it can start the cycle again. It can repeat this cycle indefinitely making it in effect , immortal.
In the country of Palau, there is a jellyfish lake with 10 million harmless jellyfish . After the lake ’s connection to the sea got closed , it left them isolated from their natural predators and so they underwent reverse evolution . These ‘ Golden ’ jellyfish have harmless stingers and so human can swim amongst them!