We have been investigating why boats float even when they are really heavy. We made mini tin-foil boats and experimented with different hull shapes to see which floated best. We also tested out how to load our 'cargo ships' to get the maximum amount of weight on them without them sinking.
Mrs Davidson did a demonstration showing how to make an egg float in water. Why not try this easy experiment at home? https://www.sciencefun.org/kidszone/experiments/floating-egg/