Miss Peppitt set Primary 6/7 the task of designing a ship that could hold as many marbles (cargo) as possible before sinking. The only material to be used was a small rectangular piece of tin foil. The children used their knowledge of bouyancy and displacement to design, build and test simple boats. All groups also made predictions as to how many marbles they thought their boats would hold. They then had the opportunity to redesign their boats after the initial marble test. Every single group managed to make changes to their boat which allowed it to then hold more marbles (cargo) before sinking.