Learning about a submarine is an excellent way to learn about buoyancy and how items react in the water. Building a submarine for a school project allows you to show everything you've learnt about buoyancy in a way that's easy for the rest of the class to understand. Gather your supplies and spend a couple of hours working to build a submarine school project. Once you build it, play with it so you can properly work it when you present it to the class.
Make three holes, each about the size of a dime, in the bottom of a squeeze bottle. Center the three holes so they run vertically in the middle of the bottle. The holes should be about ½-inch away from each other, so don't expect the holes to run the entire length of the bottle.
Tape six quarters to the bottom of the squeeze bottle. These coins will run in the same vertical line as the three holes you cut. Tape three quarters to one side of the holes and the other three quarters to the other side of the hole.
Attach the squeeze bottle lid and straw to the top of the bottle.
Add plastic tubing to the end of your straw. The plastic tubing should simply slide onto the straw. Choose enough plastic tubing so it always sticks out of the water, even when your submarine drops to the bottom of the tank.
Drop the submarine into the water. Water comes into the holes on the bottom, filling up the submarine and causing it to sink. Blow through the plastic tubing to fill the submarine with air and it will float.