Water Pressure and Depth

Water Pressure and Depth

Have you ever watched scuba divers on tv? They face many challenges when they dive. The deeper that a scuba diver descends, the more dangerous the dive becomes. During a dive, divers can experience lots of different problems. Some of these problems can be lightheadedness, joint pain, coordination loss, and even paralysis. Why?
The answer to that question has to do with air, gas, and even pressure.
Did you know that water pressure is much more dense than air pressure?
In this experiment, you’re going to observe how pressure changes with depth.

What You’ll Need:

Sharpie (marker)
Duct tape
1 clear 2-liter bottle with lid
3 in. nail with a sharp point
An adult to help


1. With the scissors; remove the label from the bottle so that you can observe what happens within the bottle.
2. Using the ruler and marker; make a mark on the bottle that’s 3 inches from the bottom of the bottle.
3. Make another mark that is 8 inches from the bottom of the bottle. Do this directly above the first mark that you made.
4. With the cap still on the bottle, lay the bottle down on a flat surface. Your bottle should now be horizontal.
5. Have an adult use the sharp nail to poke a hole into the two marks that you made on the bottle.
6. Using your duct tape, put a small piece of tape over the holes that were made to cover them.
7. Fill the bottle, clear to the top, with water.
8. You can either set the bottle at the side of the sink with the holes facing toward the sink or you can take it outside for this next part.
9. Quickly remove the tape from both holes and watch what happens!
10. What is your observation?

When the tape is removed, water will shoot out of both of the holes. The bottom hole has the water exiting the bottle more forcefully. Why?
The bottom hole is deeper under the water and therefore under greater pressure. There is more weight pressing down on the bottom so it makes the water exit with more force.

A Step Further:

For a full experiment and project, make other holes at different depths in the bottle. Test to see if the water pressure increases at a steady rate the closer the holes are to the bottom. Try using a wider container. Discover whether or not more water matters or if depth is what matters most.
You can also use salt water vs. regular water. Salt water weighs more than regular water.

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