This may be one of my son's all-time favorite activities! And while it is lots of fun outside during the summer, it is also a blast inside now!
I fill one bowl with water and give another to my son to fill with objects he find around the house.
We then cover the table with a towel and he places objects one at a time into the water. Sometimes I ask him to guess if an object will sink or float...he hasn't really figured out any means for guessing yet. And I'm fine with that. Someday he will understand all about density and buoyancy, but for now, it's all just fun and play!