User blog comment:Gcheung28/Ultimate Kaiju Battle Round 4/@comment-11132490-20130629182624/@comment-50.135.255.187-20130630004418

Technically they don't need air. Some species have the ability to absorb oxygen from the water through their skin, this allows them to stay submerged for months without surfacing. Some amphibians even have evolved external gills, but for obvious reasons Godzilla is not one of those.