We set up a science experiment using Catholic Heritage Curricula's Behold and See Grade 3. It involved a large bucket of water in the back sink dyed blue.
The girls had to push a glass jar with a dry paper towel inside straight down into the water. As long as there was no angle on the direction the jar was pushed down on, the towel stayed dry even when the jar was fully submerged.
All of these experiments so far have been great. I usually find the experiments in science books to be too much trouble to do but these are easy and really teach concepts in simple ways.
After the experiment, soapsuds were added to the water for fun,
and the Polly Pockets had a great swim.