A Japanese illustrator has offered this suggestion on how Godzilla’s anatomy might work.
The illustration reveals huge lungs so the monster can hold its breath an extremely long time as it walks the ocean floor. Serious leg bones and muscles support its 20,000 tonne weight. It has a sophisticated system, featuring a uranium sack and a nuclear reaction sack, to produce radioactive fire-breath. However do not expect any sophisticated opinions from Godzilla. It has a very small brain.