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Sadly, it is highly compressible, so air pressure would just crush the mylar ballon around it. If you could make this material rigid, so the balloon would be able to displace the proper volume of air, then you could make party balloons and airships without wasting helium.

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Wouldn't it be just as easy to make a lightweight shell around a vacuum?

Helium and hydrogen at STP are, for the most part, insufficiently different from a vacuum to make one desirable for lifting things.

So basically, what you're saying is hoverboards are possible.

No, because hoverboards are highly positively buoyant when below a fixed distance from the ground, and negatively buoyant when above it. But lighter-than-air vehicles are equally buoyant at all distances above the ground (unless you run out of atmosphere).

That's actually true of LTA vehicles, too, since the atmosphere gets progressively less dense the further from Earth you are.

It's just that the distance above ground at which the buoyancy changes sign is much, much higher :)

fit it with an altimeter so that once it is a meter above the ground it takes in air?

But they should work over water too. ;-)

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