We read a book entitled " Mr Archimedes' Bath" about Mr Archimedes who sat inside bathtub of water and found that the water rose. The animals who joined him in the bath all kept blaming each other for causing the water level to rise.
After reading the book, I asked S, how come the water rose inside the bath. He thought for awhile and said, "When you are sitting in the water, you are using the space of the water. The water will squash together, so it will go up." This was not directly explained in the storybook, so, I could see that he understood the concept.
The book was simple and did not mention about the Archimedes principle, by the ancient Greek scholar Archimedes.
"Archimedes reportedly proclaimed "Eureka!" when he stepped into a bath and noticed that the water level rose - he suddenly understood that the volume of water displaced must be equal to the volume of the part of his body he had submerged. This relation is known as Archimedes' principle."