Water Strider is a Division B and Division C event that was first run as a trial at the 1999 National Tournament. It was also held nationally in 2000 for Division B and as a national trial again for Division C at the 2002 National Tournament.
Competitors must build a device that will travel the length of a water trough, solely propelled by the carbon dioxide produced in the reaction between sodium bicarbonate (baking soda) and vinegar (acetic acid).
Unlike other building events, competitors will only be allowed to test their device once. The score is determined by adding the distance traveled in centimeters to ten percent of the total mass of the device in grams.