We used tapioca once before in sensory play (seen here~ http://funthingstodowithurkidz.blogspot.com/2013/06/edible-water-beads.html)
This time we did not use the beads but we used crushed tapioca. We cooked it one the stove with water till it started to form a gel then dishes it out and add food coloring.
The nice thing about this is that it gives you many different ways to learn. You could focus on vocabulary, 5 senses, and even color mixing.
Messy sensory play!~