Make a Cartesian Diver

Step 1: Gather Materials

get a bottle with water just below the rim,a pen and some clay

Step 2: Block the Vent

place a small piece of clay on the air vent on the top the cap

Step 3: Add Weight

add a piece of clay on the stick like thing and drop it in water it should float on the top

Step 4: Controls

put on the cap of the bottle, press the bottle to make the diver sink and let go to make it float again