Summer Fun – Water Pressure

A Production of the Ultimate Homeschool Podcast Network.

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When I think of summer fun my mind immediate gravitates to science. Yes. Science. Is. Fun.

 When my oldest two were homeschooled swimming and water activities were a great part of our homeschooling. So much so, that I convinced my non-loving-water-husband to get SCUBA diving certifications along with our kids. And, yes, it counts as science. However, we created a monster. Not my husband, my daughter. She not only adapted to a life underwater, she thrived and received her basic SCUBA, deep water and then rescue diving certifications. She even went night diving – {{Shudder!!}} While I have my diving certification I like to be able to SEE underwater.  I’m delighted to offer this guest post by Christina (Gerwitz) Moss – my daughter!

Not everyone wants to be a diver but everyone can learn some of the basic principals of diving. In this fun and free activities you can enjoy some of the feelings in your own home. And, who says you can only put on a bathing suit in the winter and swim in Florida? You can put on a bathing suit and experiment with any of these activities in a bath tub all year round in the comfort of your own home! The children will be entertained for hours with these simple activities. Of course, adult supervision is a must.

By Christina Moss 

Air Pressure vs. Water Pressure

Swimming is a great opportunity to experience pressure. As a scuba diver I have experienced pressure in both my ears and mask when descending. This pressure is felt when air gets trapped in places such as your ears and mask (if the air bubbles can escape then the pressure is not felt). Have you ever wondered why scuba divers don’t wear goggles, but face masks? It’s because you can equalize (allow air in or out accordingly) through your nose, making the pressure inside and outside the same. With goggles there is not way to let air in, therefore the goggles will simply get tighter and tighter…

You have probably experienced this when your goggles felt tight—or pressed against your face when you dove to the bottom of a pool or lake. You are feeling the air compress as you descend. Pressure is also felt in your ears. You can try this in your bathtub or backyard swimming pool.


Next time you go swimming, try this simple experiment and then the ones below. Begin by swimming down to the bottom (or as far as you can go) of a body of water. How do your ears feel? You will most likely feel the pressure building in your ears as you descend. Resurface and begin again. Swim to the bottom of the pool or lake—this time when you are three to five feet down, hold your nose and softly blowing out. This will equalize your ears making the pressure both inside and outside your ears the same. Continue to hold your nose and blow short, slow breathes every couple of feet until you reach the bottom. (Helpful hint: Start blowing before you feel the pressure.) This time your ears should not hurt and no pressure should be felt.

Now try this FUN activity with a straw and cup! You can download a science method sheet here if you want to count it as school!


Question: Where do you think it’s the most difficult to blow through a straw: into the air, just below the surface of water or just above the bottom of a cup of water?

Experiment: Blow through the straw into the air and then into different places in a cup of water.

Question: Where is it hardest to blow?

Answer: It’s hardest to blow when the straw is near the cup’s bottom.

Question: Why is it hardest to blow there?

Answer: Pressure increases as you descend deeper.

This is a fun activity to do outdoors – save those milk or juice containers! You can learn so much about water pressure doing this simple activity. You need a pencil, a milk carton and some tape. The pencil should be sharp to make holes — or use a sharp screwdriver instead.

Pressure in the Deep:

  1. Use the pencil to poke two identical holes in one milk or juice carton.
    1. Make one hole two inches from the bottom, the other hole three inches above the first.
  2. Tape the holes closed using 2 piece of tape and place the carton in a deep pan or bathtub.
  3. Fill the carton with water.
  4. Remove the two pieces of tape. As the water shoots out, look at the flow.

Question: How does the flow change?

Answer: It slows down because there’s less pressure as the water drains out.

Question: Which hole squirts farthest and why?

Answer: The bottom hole squirts farther because there’s more pressure the deeper you go.

*Note: Animals in the deep sea live in pressure that is a hundred times greater than we live in on land. Animals survive such forces because only the gas spaces in animals’ bodies are crushed by pressure. Water and most oils don’t compress under pressure.

Changing Colors:

Scuba diving has offered me many opportunities to learn about scientific facts and witness them firsthand. Having been to 120 feet (advanced certification is needed) allowed me to see the slow continual decrease in color. Several factors contribute to the fact that there is less light the further down you descend. One reason is that some light reflects off the surface, secondly some is scattered by particles in the water, and finally some is absorbed by the water itself. The absorption process, however, is not consistent. Sun light consists of many different colors mixed together. Each color is absorbed, one at a time, as you descend in this order: Red, Orange, Yellow, Green, and Blue. Many divers carry flashlights which restore the true color of different objects and sea life.

  1. Experience the color changes that occur as if you were a diver 100 feet (30 meters) under water.
  2. Look at objects of various colors through filters made of colored plastic. You can use disposable colored plastic containers or colored clear wrap (red and green is sold in stores at Christmas time).


Question: Which colors disappear in blue light?

Question: What happens to the objects when you look through a red or dark green filter?

Question: What happens to the colors and why does this happen?

Experiment with the blue-colored plastic.

Question: What colors would best help deep sea animals blend in with their surroundings?

Answer: The color red looks black in the deep sea because it has all been absorbed. If you look at deep sea animals, many are red and black!

The Bends:

The Bends also known as Decompression Sickness sometimes afflicts scuba divers.  As divers found ways to descend deeper and stay underwater longer while breathing compressed air, they began to suffer a new and at the time unexplained sickness. After returning to the surface, divers sometimes would experience dizzy spells, difficulty breathing, or sharp pains in the joints or abdomen. The diver would usually recover after a period of time, but in some cases might never be completely free of some of the bad effects. Today decompression chambers are used to treat the sickness. The bends are caused when you are underwater too long and excess nitrogen begins to form bubbles in your blood vessels and tissues when you ascend. This can be prevented by not exceeding your “no-decompression” limit, which is found on a dive planner. A No-decompression limit is found by calculating how deep you will dive and how many minutes you will be down. For example if you were diving to a depth of sixty feet you could stay down for no longer then 55 minutes. If you plan to make several dives there are other factors to consider. Diving is a very safe sport as long as you follow the rules! All dives are planned before you descend. *Note: Many of the most beautiful reefs are between 25-40 feet down (in the Keys) which means that you could conceivably stay down for 205-140 minutes, which is impossible due to air consumption (unless you have two tanks)!

What Happens when you get the Bends?

1. Materials: two bottles of carbonated drink and two glasses.

2. First, pour one drink into a glass very slowly, so that the bubbles can escape a few at a time.

Bottled up gas is under pressure and remains dissolved in the liquid. When you open the cap and the pressure is released, the gas escapes in the form of bubbles. In carbonated drinks, the gas is carbon dioxide. The gas that is released in a diver’s bloodstream is nitrogen, which makes up about 80 percent of ordinary air. If a diver rises slowly to the surface, the pressure changes slowly and the gas is released slowly and safely.

  1. Now pour the other bottle of soda quickly into the other glass.

Question: How does it foam? Hear it hiss?

Answer: A reaction similar to this takes place in a diver’s bloodstream if he comes up to the surface of the water too quickly, causing a painful or even fatal reaction.

Make a Diving Bell

  1. You will need an empty glass and a larger bowl or pan of water. (A clear glass works best).
  2. Hold the glass upside down and push it down into the bowl of water.
  3. Be sure to keep the glass level so the air bubble won’t get out.
  4. Notice that the pocket of air stays trapped in the top of the glass even when the glass is completely underwater.

The first diving bells were this simple. The diver inside breathed the trapped air.

Whatever you do keep learning! I’ve had fun SCUBA diving and perhaps someday you can try it as well!

Truth Seekers Mystery SeriesChristina Moss is Felice Gerwitz’s daughter (the owner of this site) and co-author of the Truth Seeker’s Mystery Series. Christina was homeschooled K-12 and attended FGCU in Ft. Myers graduating in three years with honors. She is a homeschool mom of five and soon to have her sixth. She is married to Bill and lives in Florida.

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