The above figure is a bathyscaph. The bathyscaph is the object outlined in red. It is in a tank full of water. The bathyscaph is a sealed container with two holes in the bottom. One hole allows water to enter and the other is attached to a rubber hose that allows the person to blow air into or let air escape out of. The tube in the bathyscaph, which is attached to the air hose must not go below that water level inside the bathyscaph. The bathyscaph is an excellent visual aid to describe buoyancy.

We placed the bathyscaph into a glass aquarium filled with water. As the water went into the bathyscaph, the bathyscaph sank. Tony then blew air into the bathyscaph causing it to rise. While he was doing this I explained why it was rising and sinking, again reinforcing the concepts of why an object floats.

An excellent example that works on the same principles as the bathyscaph is the submarine. When we told the students that submarines work on this idea, once student was very upset. He was worried about what would happen to the people when they let in the water to allow the submarine to sink. How can you possibly not love children?

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