1. Remove any labels from your bottle so that you can watch the action.
2. Fill the bottle to the very top with water.
3. Place a small pea-size piece of modeling clay at the end of the point on the pen cap. (see drawing)
4. Slowly place the pen cap into the bottle, modeling clay end first. (some water will spill out - that's okay) It should just barely float. If it sinks take some clay away. If it floats too much add more clay.
5. Now screw on the bottle cap nice and tight.
6. Now for the fun part. You can make the pen cap rise and fall at your command. Squeeze the bottle hard - the pen cap sinks...stop squeezing and the pen cap rises. With a little practice, you can even get it to stop right in the middle.
1. Does the size of the bottle affect how hard you have to squeeze the make the diver sink?