The Fitness Fixer
The Fitness Fixer

Living Under The Sea

Since I was small, I wanted to be a scientist. I wanted to study physiology under the sea. I wanted to live underwater, and for a time, I did. This is how I found out about exploding toilets.

I grew up to be a scientist in extreme physiology - the science of surviving extremes of heat and cold, mountain top and underwater, high and low air and water pressure, exercise and nutritional and pharmacologic tinkering, altitude, g-forces, injury, and other things extreme.

One of the laboratories where I worked was tethered to the bottom of the ocean at a moderate depth. It was a small metal building with air inside. You could not see it from the surface. If you went by in a boat, or drove by the highway, you would see only the sea. We wanted to order a pizza and give the lab address and see the delivery person pull up to nothing but water and try to find us at the bottom of the sea. Even scientists can be funny sometimes.

To live in the lab, we swam down in scuba gear, entered through a small hatch in the bottom, and dried off, or just walked around in a towel. Then we stayed dry while working and sleeping inside. We walked around normally and breathed the air normally, day after day. When it was time to go to work outside in the ocean, we put on scuba gear or surface-supplied hoses, and swam down through the bottom hatch. The hatch did not need to stay closed. We could look down to see fish swimming, even sit on the lab floor and dangle our feet in the water through the hatch, without flooding the lab. How does this work? See the drawing at right of an elementary science demonstration:

  1. Hold a glass upside down over a bowl of water.
  2. Push the upside down glass straight down into the water.
  3. Water doesn't enter the glass. Water rises in the glass a small amount because air is squeezed by water pressure. As long as you don't tilt the glass too much, the rest of the water stays out.

It works pretty much the same way in an underwater laboratory, summarized in a child's science homework at right. Water stays out and air stays in with everything dry inside, as long as a sea monster doesn't come and knock the lab sideways.

The deeper the lab, the more the air is squeezed and the higher the air pressure. If you bring something full of air down to the lab, it might squash flat by arrival. One of the scientists had a CD-player that I brought down for him in a transfer pot. We opened the pot to find the case bowed inward, so tightly suctioned from inside that it couldn't open.

When transferring gear back up from the lab to the surface, air expands as water pressure decreases. Water-tight cameras had to be transferred open, or they might pop on the way up.

This same "pressure-volume" gas-law relationship applied to the marine toilet, a rectangular plastic box with a screw cap lid. When coming up, air expands. From only 33 feet of seawater (10 meters) to the surface, air volume will double because water pressure is decreased by half. Unless you fill the toilet box completely with water (or other liquids and solids), all gas inside will expand on the way up. It was a test for new interns to see if they understood gas laws to prevent the toilet from expanding enough to explode. Good to understand Boyle's Gas Law.

Related posts on better health and improving fitness in extremes:

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About the Author


Dr. Bookspan is an award-winning scientist whose goal is to make exercise easier and healthier.