Building a homemade submarine is a school project that teaches principles of gravity, pressure, friction and buoyancy. It can also be an economical project that uses common materials and one that does not require special skills or large amounts of time to complete. You can craft a submarine while learning to understand why these machines are able to move up and down in the water.
Cut three small holes into one side of the soda bottle. The holes must be equally spaced at least one and a half inches apart. Dot the areas to be cut with the black marker.
Stack the quarters into a group of four and the nickels into a group of four. These stacks will serve as weights. Wrap each stack of coins in the adhesive tape, tightly securing the tape around the coins. The stacks must be firm.
Place the rubber bands around the plastic bottle, putting one just beneath the hole that is closest to the bottom of the bottle and one beneath the hole that is closest to the top of the bottle. Position the four-quarter stack under the rubber band that is closest to the bottle's bottom and the four-nickle stack under the rubber band that is closest to the bottle's top. The weights should be next to the holes but should not cover up the holes.
Remove the bottle's cap and insert the shortest end of the straw (about an inch long) into the opening. Mold the clay around the opening, making sure the area is sealed from water entering and that the straw is secure with its long end bent upwards.
Lower the submarine, with the weights facing down, into the bowl or aquarium. Let the bottle fill up with water, but not through the long end of the straw. The top of the straw should not go under the water. When the submarine is filled with water and stops sinking, blow into the straw. Observe the actions of the submarine and record them in your notebook.