They start out tiny.
We put them into our sensory tub and added a litre of water. Very quickly they began to get bigger. We noticed that when we added more water so that the water was covering the beads, the beads seemed to 'disappear' into the water. It was only when we shook the water or swirled it with our hands that the beads became visible again.
The beads felt slippery and slimy!
We counted them and tried dropping them into the water from high!
The beads release water very slowly so we are leaving them in a colander to see if they get smaller.