The first week we tested different objects to see what would float and what would sink. Some things were tricky like the plastic spoon. It floated at first but if it got water in it it sunk.
The next week we put a plasticine ball in the water and it sunk. We thought about how heavy things sink but ships that are made of heavy metal float. So we tried to make our plasticine like a boat and guess what? It floated too! But you had to make it carefully because it let water in easily.
It could float because we’d spread the heaviness out and it held air-like a ship.