Filling objects with colour?

I've just started my bright Asperger Syndrome child on Alice, as part of home schooling, and it's going very well. But I'd like to incorporate some work on water and nutrition we've had sent home from school by creating an animation that fills an object representing the human body up to the proportion comprising water - ie, around 60%.

Any tips on how to go about this?

This may not be much, but here's an idea...
Why not create a world with some sort of open container, like a box or something, make a square or something with a water texture, and program the square to climb up inside the container proportional to about 70% of the container? I know this idea is pretty simple, but it would probably be a good place to start...

Lemme know how it works!

Thanks. It might take a little fiddling around - we're novices, he's quicker than me - but that's a good start.