A hundred ton steel ship floats, a hundred ton steel block does not. Density equals weight per volume. If you increase the volume without increasing the weight, the density will go down.
Exactly my point, the volume doesn’t change in the example provided. Weight and volume stayed the same. We either need to expand Godzilla or it needs to eject some mass.
I think that it’s implicit that the volume of Godzilla would increase; we need to assume that the bounding layer has a degree of elasticity and that that the matter displaced by the flotation cavity will expand into that, reducing the net density.
Mighty Godzilla, with power untold
Rises through the waves; his powers unfold
Hidden muscles in clever design
Create a new chamber as they realign
Inflating his body, a titanic display
Defying the depths, he floats up and away
No long bound by the oceans’s might
Godzilla soars, a triumphant sight!
Yes, that would work. But imagine the swelling, to give Godzilla that much buoyancy.
In the example he gave, he mentioned lungs expanding, so volume IS changing. Godzilla can shoot lasers in current lore. He could easily have some super compressed ballast tanks as organs that release pressure changing a whole slew of variables.
If Submarines have ballast tanks of 600 pounds of air at 3000 PSI, Godzilla can have his own magic organs that do crazy stuff.
Expansion of lungs makes us float because our whole body expands significantly, relative to our small volume.
In the examples mentioned above, the organs creating vacuum are said to be “somewhere inside” the body. Vacuum or not, Godzilla needs to visibly swell to increase its volume and bouyancy, which we don’t observe.
The air in submarines is used for pushing the water out of tanks, so the principle is ejecting matter. If Godzilla were to use that approach, as I said before, it needs to eject something.
