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Polluted Runoff: Nonpoint Source Pollution

Darby Duck, the Aquatic Crusader - Speedboats

Ever wonder how things can move in the water?

Try this!


  • large, clean bowl of water
  • thin cardboard (index card or notebook cover)
  • scissors
  • liquid dish detergent
  • pencil


  1. Draw a triangle on the thin cardboard
  2. Cut out the triangle-shaped boat and float it on the water near the edge of the bowl.
  3. Put a drop of liquid detergent on your fnger.
  4. Gently touch the water behind the boat with your soap covered finger. What happens?
  5. If you want to do this again, you need to get new water that has no detergent in it.

How it Works

The detergent on your finger weakens the surface tension of the water behind the boat. There is still strong surface tension in the front of the boat so the boat is pulled forward.