You remember that expanding gel stuff? Well, i thought the trouble with it was that somehow, you'd still have to get all the water in, so in practical terms it isn't really any different than just inflating someone with water.
Anyway, i'm going to have a go at explaining another idea i've had.
This is a video of something called a Hoberman Sphere:
http://www.youtube.com/watch?v=3r4x5jRca20
Suppose there was a way of making either nanomachines which were that shape or molecules joined together, and they were made into some kind of fluid or mixture.