why is this useful, there is no fluid to submerse a craft into in zero gravity environments

@@salamanderproductions2104 in our EE and physics courses in college, elec engr majors were taught "electromagnetic waves do not need a medium to propagate" If you work at artificial gravity devices, a first step is to look at clues/evidence for the idea that "space is empty" is incorrect (because it IS incorrect) *A PHYSICAL ANALOGY* Ed is a college student who was never taught the atmosphere consists of invisible gases. Ed volunteers at a research project for a few bucks. 1) "Ed, you're a college student, welcome to our research project" 2) 'This room has transparent Lucite walls - step into the room and we will take your vital signs" ED: "The room looks fine - I'll step inside" Ed has never seen the air he breathes, after all, and he steps into the room. It is an evacuated room with no air. That analogy is the state of common physics. The intellectual hurdle of getting past the 'space is empty' belief is high. But to build artificial gravity devices, you have to learn how: 1) matter couples to free space 2) take the opportunity to operate on the matter to change its coupling to free space .

You'd probably need to calculate the average density. If a box is 95% air, and 5% plastic (the box is made of plastic), the density would be mostly the density of air. The calculation would be: total density of the box = (0.95)(density of air) + (0.05)(density of the plastic) The 5% of the box density that is plastic is the reason the box would not float away, above and off the surface of the water.

Thank you very much, I was flabbergassed when I didn't had the same result as him.

Yup! Any object that is submerged means it has displaced some amount of fluid. And that displaced fluid is what causes the buoyant force to push back upwards on the object.