EXPERIMENT
Slip the hex nut onto the stem of the pipette and slide it upward until it stops. Screw it onto the base of the bulb. A few turns will hold it in place. Cut the stem a quarter-inch above the base.
Pour about 4 inches of water into the large plastic cup. Test-float the diver in the cup. It should bob up and down with the bulb sticking out of the water. Squeeze the bulb and draw some water into it by releasing your grip. Repeat this several times until the diver is half-full with water.
Let go of the diver to see if it still floats. When properly adjusted, the diver should just barely float in the cup of water. If the diver sinks to the bottom, grab it, squeeze out a few drops of water, then re-test it until it floats properly.
Fill the soda bottle all the way to the brim with water. This is VERY IMPORTANT! Place the diver in the bottle, but be careful not to lose any of the water inside the diver or out of the top of the bottle. If you do, you’ll have to test-float the diver again!
Put the cap on the very full soda bottle with the diver inside! Squeeze the sides of the bottle. Does the diver sink? You may have to squeeze very hard with both hands, depending on the water level in the diver. What happens when you release the squeeze?