The children in our school explore the properties of water and the properties of "things" in the water frequently.
They've moved quite a bit beyond evaluating whether things will "sink or float".
However, one day, as they were trying to find something to carry their animals and vehicles as a boat, I observed a first in our school. After some discussion and some experimentation with various blocks that float, they decided to try...
...paper!
And it worked...
...briefly...
...but not for long!
So, they crumpled up the paper...
After trying one more time, they moved on! I wonder when I will observe this experiment repeated.