Above: Image © ultramarinfoto , iStockphoto.com

Want to learn to Scuba dive during your tropical getaway this winter?

The most important rule you will learn when Scuba diving is that you must never hold you breath! You might think breathing continuously would come naturally – I mean you are doing it right now. But holding your breath is actually a common problem for new divers!

Did You Know?
Scuba is an acronym that stands for "Self Contained Underwater Breathing Apparatus". The name describes the system that first allowed divers to go underwater without being connected to a surface air supply.

Here’s why it’s important to keep breathing while you’re diving.

While you don’t notice it, the weight of the air around you is pressing down you on. This is called air pressure. On land, air pressure is consistent at one atmosphere or 14.7 pounds per square inch (psi). Because water weighs more than air, the pressure increases as your dive goes deeper, due to the weight of the water above you. Every 10 metres below the surface exerts the same pressure as one atmosphere, so when you descend 10 metres, you would be under two atmospheres (29.4 psi) — one from air and one from water. If you continue to descend to 20 metres, you would be under three atmospheres of pressure and soon.

Image inspired by those in PADI manual on page 17 & 19. Created by Sarah Jenkin using Concept Draw Pro.

There is an interesting relationship between pressure and volume, and it’s a gas law called "Boyle’s Law". This law states that pressure and volume are inversely proportional – so as pressure increases, volume decreases. So, if you had an empty container that was open at one end and brought it to a depth of 10 metres (increasing the pressure), the volume of air in the container would decrease by half. The opposite would be true when you swim to the surface.

A balloon filled with air at the bottom of the ocean would expand and likely pop as it floated to the surface, because the volume of air inside it would increase with the decreasing pressure. The same would happen to your lungs if you went to the surface without releasing the air from them by breathing out. This can cause lung over-expansion, which is a very serious injury. But it is a very easy injury to avoid — you just have to remember to breathe!

Did You Know?
Common symptoms of over-expansion injuries include numbness, loss of hearing, vision, or speech, chest pain,difficulty breathing, unconsciousness, and death.

Pressure can also impact your ears. When you dive, the increase in outside pressure pushing on your body causes your eardrum to curve inwards,which can be very painful. You may have experienced a similar discomfort when taking off in an airplane. You can equalize this pressure by blowing against your closed nose. This increases the pressure inside your ear, bringing it closer to the external pressure.

While pressure can affect you underwater, a few tricks, such as swallowing or moving your jaw back and forth, can help keep things equalized.

Did You Know?
You should never dive when you have a cold. Blocked sinuses can make equalization impossible.

Once you learn the proper techniques — and remember to keep breathing — scuba diving can be a lot of fun, opening up a new underwater world to explore.

Learn More!


Introduction to General, Organic and Biochemistry. 2009. Bettelheim, F. A., Brown, W.H., Campbell, M.K., Farrel, S.O.Cengage Learning, p 144.


PADI Open Water Dive Manual. 2002. International PADI. Rancho Santa Margarita, CA. pg 13-27.

Scuba diving:a Trailside Guide. 2000. Berger, K. W. W. Norton & Company. pg 126.


Article first published on October 15, 2010.

Sarah Jenkin

I am currently working on my M.Sc, which focuses on how temperature and oxygen levels change breathing rate. But what is really cool is that I look at breathing just from the brain. I have worked in a lot of different areas, from training toads to distinguish between black and white stimuli, to flying in helicopters while wearing night vision goggles, to SCUBA diving with robots. I love adventure, especially when it also involves travel to a fun new location I love music, candy, and long walks on the beach.

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