Provide a bucket of water and a large lump of clay. Form the clay into a large ball and drop it into the bucket; it plummets through the water to land on the bottom of the bucket. Have the elementary students use balls of clay to form different designs of boat, including canoes, rafts, barges and clipper shapes. Try each type of design on the water and see which float and which do not. Discuss why some designs work better than other designs. Consider why the ship shape floats and the ball does not. Alternatively, experiment with adding air pockets as ballast.
Take a 16-oz.,capped, empty soda bottle and a 2-ltr. empty, capped soda bottle. Lay both sideways on the water and push down to submerge. Ask the class which takes more pressure to stay submerged. Cut a wide oval in the side of the bottles from bottom end of the bottle to where the bottle narrows toward the neck, creating a boat-shaped object. Load each boat with coins or ball bearings, one at a time. Take note of which boat sinks under the load first. Compare the loads proportionally to see which size is more efficient. Discuss why a bigger surface area on the water allows the boat to carry heavier loads. Alternatively, experiment with the size hole to see whether larger or smaller openings increase the ability of the craft to float
Many movies or television shows that have a shipwreck scene onto a deserted area have the characters try to build a raft to get back to civilization. Using twigs and plant vine, have the class members try to build a ship or raft that will provide transportation. Encourage students to think about how to keep the craft afloat and keep the people and supplies from washing overboard. Consider available materials, such as native plants, flotsam on the shore and whatever the survivors rescued from the ship to equip the craft with a sail, oars and keel. Alternatively, consider other ways to construct a ship, such as hollowing a large trunk to make a canoe.
In Exodus 2:1-4, the Bible explains how Moses’ mother made an ark or tiny boat of bulrushes and pitched it to make it waterproof. Junior and senior high school students explore using various ways ancient people made a structure watertight so it would float. Students can try different recipes for pitch to waterproof the boat. Alternatively, students can try more modern substances and methods to make a craft watertight. Compare options in terms of cost and effectiveness.