Garden Eel

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• Materials required: bendable straw, nut, rubber balloon, thick rubber band, wide-mouth plastic bottle
• Attach a weight, such as a nut, to the bendable straw. Stuff tissue paper on the opposite side of the straw and cover it with glue. Then, add a stripe pattern of your favorite color.
• Next, build a garden eel nest. Glue the board with a hole on top of the cylinder. Place a weight under the cylinder.
• Float the garden eel in the water and adjust the amount of water in the straw so that the head is slightly above the water surface. Put this in a wide-mouth plastic bottle containing water.
• Cut off the mouth of the rubber balloon, put it over the mouth of the wide-mouth plastic bottle, and secure it with a thick rubber band. Work in a bucket filled with water to prevent air from entering.
• Press the rubber membrane of the mouth with a ping-pong ball. Then, the garden eel will pull in, and if you do not press as hard, it will come out (if you do not have a ping-pong ball, you can press with the palm of your hand).
• Pressing the mouth of the plastic bottle increases the pressure of the water and air inside it. The air gets compressed and the volume decreases, so the buoyancy is reduced and the garden eel gets pulled in. Conversely, if you do not press as hard, the air expands, the buoyancy increases, and the garden eel comes out of its hole.

[Keywords]	Pressure, buoyancy
[Related items]	Floating and sinking squid, Cartesian diver
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, p. 42–47.

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