The exercise was quite simple:
Put the stones into the bottle to make it sink to the bottom of the tub.
Put a balloon into the bottle and blow into it to make it rise to the top.
Oh - and don't forget to make you submarine "cool" be decorating it with stickers
My main goal with these children is to entice them away from staring at ipad screens and use their hands and creativity to interact with the physical world making things. For one afternoon, at least, I was successful :)