The children conducted experiments by placing various objects in water to understand why large boats can float without sinking in the sea. They learned that metal does not float on its own but will float if it contains air inside. Wood floats well regardless of its orientation and does not need an air chamber. The document then lists several other objects tested including plastic, clay, boxes, scissors, balloons, paper, toys, fruit, and describes whether each object floated or not based on the materials it was made of.