I think this is the logical conclusion a lot of kids come to in science class when learning about buoyancy. I remember asking about the idea and being told the container would have to be too heavy in order to resist the forces. I suspect the real answer is much more complicated. I wonder about the actual possibilities that come with modern material science.
> A vacuum airship, also known as a vacuum balloon, is a hypothetical airship that is evacuated rather than filled with a lighter-than-air gas such as hydrogen or helium. First proposed by Italian Jesuit priest Francesco Lana de Terzi in 1670
and also unknowingly re-invented by me a long time ago... sad it's still in the 'hypothetical' stage