We used them for our high school science and math classes. They worked exactly as we wanted to poke holes in them so we could show how gases can build up and exert a force on an object in a liquid (water in this case). Fins were made from a small piece of duct tape and thick construction paper to help the "boats" move in a straight line, while the alka-seltzer reacted internally, creating a gas that propelled them forward.
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