The kids call "squidy" their new pet. On command Squidy will dive to the bottom or swim to the top of the soda bottle.
To make Squidy work you have to use a pipette, a hex nut. You have to build the diver(pipette) by squeezing just enough water in the pipette and then you must test float it to make sure it works. Then you fill a soda bottle all the way to the brim. Put Squidy in the bottle and squeeze the bottle with both hands and tell Squidy to swim or dive.
The original Cartesian Divers were made out of glass medicine droppers or delicate glass ampules. My kids love this experiment all week they were independently doing this experiment, trying really hard to get the water levels right to command Squidy to swim or dive. I am happy for this experiment because I saw them actually using the scientific method every step of the way, and now they know "Sink or Float " is still an experiment to explore at deeper levels.To see other science activities that children are doing go visit Adventures In Mommydom.