I don’t think so. But I do know that there are at least ten species of large animal still undiscovered in the ocean depths (we can estimate this from looking at the rate we have been discovering “sea monster” species in the past).
Now here’s a question back: who do you think would win in a fight between Godzilla and the monster from Cloverfield?
The story is that he was formed from a mutation due to radiation from nuclear fallout. Mutations due to radiation are possible, and have been found in both humans and other animals in the areas surrounding Chernobyl in the Ukraine, where there was a massive explosion at a nuclear power station in 1986. None of these have resulted in a godzilla-like monster though, mostly just in a rise in birth defects in the children of survivors. 🙁