So, mass and density are functions of weight on a Flat or Globe Earth, but on The Globe Earth you have the extra "layer" of Gravity applied to all mass and density, creating a "stick to the ball" effect, which explains how trillions of tons of water can stick to the side of The Globe Earth and a seagul can still fly over that water. I think somehow Gravity is supposed to attract objects corresponding to their mass and density. So, Gravity "can" hold all that water and still let the seagull fly. I don't think Gravity is real, but I think that is roughly how it is supposed to work.
Of course, there is the further "layer" of The Earth's spin, at around 1000 mph. Gravity is supposed to hold us safely to The Globe Earth, while this spin is occurring. Again, mass/density don't explain why we don't fly off/fall off a Spinning Globe Earth; Gravity explains that.