Yes, I named it that just so you'd giggle.
Here's what to do.
1. Get a bowl or bin and fill it with water. You can use a bathtub, kiddy pool, or sink.
2. Randomly grab little things you don't mind getting wet (spoon, feather, sponge, pennies, whisk ... probably best to hide your cell phone about now).
3. Show your child how some object float and some objects sink.
4. For each item, have your child guess if it will sink or float.
5. Test your hypothesis!
To make this easier for younger kids:
Omit the guessing and just play in the water with toys that aren't usually water toys.
To make this harder for older kids:
1. Talk about mass and density. Need a refresher? Look here , among other places.
2. Blow up a balloon and talk about why it floats.
3. Put a plastic margarine container or toy boat in the water and add pennies or marbles until it starts to sink. Have your child guess how many of the heavier item it will take to sink the boat!
**NEVER, NEVER, NEVER LEAVE YOUR CHILD UNATTENDED WITH WATER**