In this activity (on page 2 of the PDF under GPS: Sailboat Design Activity), learners will discover how the shape of an object, not just its weight, determines whether it floats or sinks. After a ball of aluminum foil sinks in a bucket of water, the ball is opened up into a flat sheet that learners will shape into a sided tray or another shape they may come up with, then placed back in the bucket. If it floats, carefully add pennies until it sinks. Relates to the linked video, DragonflyTV GPS: Sailboat Design.