The shape of an object can help it to float or cause it to sink. Try this Put a lump of Plasticine the size of a golf ball into a bowl of water and watch what happens. Click 1 Now make the Plasticine into the shape of a boat and watch what happens this time. Click 2 The boat-shaped Plasticine pushes down on a bigger bit of water. The water can push up more of the Plasticine and hold it up so the boat floats. The lump of Plasticine pushes down on a small bit of water so it sinks. topicresources.com