Balloon Fish

A fish that when born is instantly filled with helium from it's helios gland that makes it float up and fly out of the water due to being unable to breathe it dies and explodes it then releases millions of eggs which will hatch after a week and suffer the same fate.

Balloon Fish offspring are a exact clones of their parent.

If by chance the balloon fish is kept alive longer than a year nuclear fusion will occur inside it's Aurum (a special organ that only the balloon fish has) and gold will be produced which weighs down the fish so it can survive.

The Balloon Fish never got to produce the gold it needed to survive.