What happens when you push a balloon full of air into a body of water, that's in space?

My 8-year-old son asked this question and i couldn't give him a definite answer. So he's wondering if it would do the same thing as a balloon pushed underwater in the bathtub (which kind of makes sense to me, due to the density differences, not just gravity alone).

But I told him I'd ask those more knowledgeable than me.