Interestingly, despite UY Scuti's insane, astonishing, mind blowing diameter... So vast that they call it a "hyper-giant-star"...

It is actually "only" about 8 to 10 times the total mass of our sun, give or take, if I recall correctly.

Which kinda means it's probably transitioning from a star to something more like an insanely inflated puffy "fluffy cloud" of hydrogen and helium, I suppose you could say?

But ya, its density is so low that it would proverbially "float in water" if you had a giant cosmic bathtub.

Of course: in reality the mass of that much water in such a hypothetical bathtub would gravitationally suck in the star, and merge with it, and probably would then form a black hole.

But ignoring that factor... ya, UY Scuti would totally float in a bathtub no problemo!