Resources: Experiments - Make Your Own Submarine

Build your own submarine. Discover the principle of buoyancy in your kitchen sink or bathtub!

All you need is:

• a plastic soda or water bottle with cap (any 16 oz, 20 oz or 2L bottle will do)
• a flexible straw
• modeling clay
• adhesive tape
• 7 quarters
• 2 rubberbands
• bathroom tub, kitchen sink or large bucket filled with water
• aluminum foil

Here's what you do:

Empty the bottle and make a hole in the cap large enough for the straw to fit through (This is easiest to do with a hammer and large nail, so ask an adult to help). Now make two holes in line with each other along one side of the bottle. Tape the quarters together in one group of three and one group of four. Using rubberbands, secure the 4-quarter group below the hole nearest the bottle's bottom and secure the 3-quarter group underneath the uppermost hole. Fit the shorter end of the straw through the hole in the bottle's cap and seal with modeling clay. Put the cap back on the bottle.

Hardsuit getting wet in the open ocean for the first time.

Now, fill up the bathroom tub, kitchen sink or large bucket with water. Hold your "submarine" underwater so that it fills with water and sinks (be sure to keep the open end of the straw out of the water). Now, blow into the straw and watch what happens.

Here's how it works:

The submarine filled with water has negative buoyancy and is denser than the surrounding water, so it sinks. As air is blown into the submarine, it gains positive buoyancy and is less dense than the surrounding water, so it rises. Do the next experiment "How Does a Submarine Dive" to learn more about buoyancy and submarines.