Godzilla is a mutated genus of Godzillasaurus from the Triassic Period, his origins are unknown location-wise, however some believed that Godzilla was a marine reptile rather than a Dinosaur before his radiated mutation state. Getting the Wiki-like description out the way, it's MY turn. In this world, Godzilla wouldn't be likely to survive if he existed as the movie variation, however a Redditor (Name is in credits) made a variation whereas Godzilla was made to fit into the real world, giving him more visible webbed hands, and putting him in the amphibian animal class instead of reptilian, and so on and so forth. also, Atomic breath may not be accurate but basically, the Godzilla species has a methane bladder which holds methane, a flammable bodily gas, he releases the methane through his mouth, he then uses his electric eel electric pulse to ignite the methane and boom. An Ignited breath, the result may not turn out blue but atleast we know an animal can be capable of fire breath.
Credits to Speculative Evolution on Reddit If you want specific info just look up "Godzilla but he's way too realistic" Music: Godzilla Theme (Blob Opera)-JimmyGpianotutorials