We tested different things to see what floats and what sinks after we had a guess first. Sometimes we were surprised. We didn’t think the heavy, big block of wood would float but it did. Objects that floated were made out of wood or sponges or really light thing that didn’t let water in or that had air in them.
Things that sunk were metal things or golf balls or hard rubber or plastic things.
We made boats out of plasticine and they could float but it was tricky to make them.