It really doesn’t matter what age you are, we’re sure you remember baking powder submarines. That’s because cereal manufacturers have been including them as prizes since the advent of injection molded plastic. Fill them with baking soda and take them in the bath with you. They gently dive and surface. The problem is that the cereal prizes were tiny. Now you can relive your childhood with an adult size version of your own making.
The submarine is basically a hunk of PVC with a conning tower to keep it upright and a chunk of hose into which the baking powder is placed. The idea is that the powdery acid and base that makes up the stuff reacts when hit with water. This gives off a bit of carbon dioxide, which makes the sub float to the surface until the bubble escapes and is replaced with water to again sink the ship. The difficult part is to find the right buoyancy (using wine bottle cork) so that the bubble is all it takes to oscillate between the surface and the watery depths.
Watch it go in the video after the break.