General relativity, which describes the effect of mass on space-time, is a very elegant theory with beautiful maths. The trampoline and ball have incidental similarity, but they're for illustration only.
There's nothing that makes the waterbed theory necessarily wrong, but you'd have to posit some new maths different and more complicated than we have with GR.
There's nothing that makes the waterbed theory necessarily wrong, but you'd have to posit some new maths different and more complicated than we have with GR.