Under Water Pressure in Scuba Diving

scuba diving pressure

scuba diving pressure

Have you ever seen that movie, Waterworld? I hope so, because I’m about to use that as an example. In Waterworld, Kevin Costner is without a single shred of diving equipment. Costner’s character jumps to the water and submerges to the deep parts of the ocean so fast; he could’ve saved half of the drowning passengers in Titanic.

An experienced scuba diver knows that Waterworld is deceitful in its presentation of people who descend to the oceans at great speed. If the vital element of pressure was taken into account in this movie, Costner’s character would’ve felt a painful, dying sensation crushing his body, ear drums, and the rest of his air cavities. His lungs would then collapse and life, as you know it, will end faster than Paris Hilton’s acting career.

A competent knowledge of pressure, and how to control it, is something that should be stamped into the scuba diver’s will to live. To secure this knowledge, it is in my own misfortune to tell you that the bloody wonders of Math must take part in this article for us to truly understand what underwater pressure is all about.

But before we numb ourselves with the necessary numbers, we have to discuss  some facts about underwater pressure. On land, we are under a great deal of air pressure. But that’s okay, because air is relatively light. When we dive in the ocean, we are under the influence of water pressure. We don’t need a scale to tell us that water is heavier than air. The ocean is a lot of water, and if the scuba diver wishes to reach the ocean depths, his body must have the ability to withstand all that water above him.

If you really want to master the act of controlling water pressure, well prepare to get a pen and paper cause we’re about to get arithmetical.    A cubic foot of air weighs approximately a pound and a half. Water, on the other hand, weighs just about 62.5 pounds per cubic foot. But the ocean is not composed of water, but sea water! So a cubic foot of sea water, thanks to salt, weighs an extra 1.5 pounds.

The more a scuba diver submerges himself underwater, the more the pressure increases. This type of pressure is called, “atmosphere of pressure.” The atmosphere of pressure is labeled as ATM, and is measured at 1 ATM at sea level. The ATM increases by 1 for every 33 feet a diver plunges into the ocean depths. So, if my ability to multiply still functions, 66 feet below sea level equals 2 ATM. It is also said that the diver can calculate the pressure’s effects to his body by using Boyle’s Law. My mathematical comprehension chooses not to torture itself by exploring this madness.

If the diver descends from sea level, he must not be too anxious to reach his destination- Because if the scuba diver hurries his descent, he might not live long enough to experience his ascent. Do not be sad, you don’t have to finger paddle yourself all the way down. You just have to be very careful in the first 15 feet of your dive. Be slow to dive, so your body can adjust to the pressure. During this time, you will feel a slight squeeze within you body. Once that feeling has disappeared, you’re good to go. But remember, during your way up to the surface, the same principles apply.

We don’t want any scuba divers going home with collapsed lungs or an exploded ear drum, or even worse, two exploded eardrums. So it is wise for the scuba diver not to let the preceding facts about pressure left neglected- Especially if you’re one of the guys who were responsible for making Waterworld.

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  1. Wrong! 33 feet is two (2) ATM and 66 feet is three ATM this is because you have 1 ATM of air plus two ATM of sea water pressing on you when you are diving at a depth of 66 feet in the Ocean.

  2. I might also add the speed at which you descend ( go down) is variable for each individual and highly dependent on how well their system equalizes ie air passages between the nose, ears, eyes and throat. I personally can crash dive to 60 feet with no need to do a Valsalva maneuver but then I have logged in excess of 30,000 dives so my air passages are very elastic. I caution that the opposite however the Ascent (going up) is not as flexible, everyone should never never rise to the surface faster then the recommended 30 feet per minute rule ( this is a change from when I was trained in the Navy back in 1979 when the rule was 60 feet per minute).

  3. He was free diving numb-nuts.

  4. You do realize his character had gills. Your argument is invalid.

  5. All of the above having been said, free diving, gills. ect. everyone really missed the worst math. THe top of Mt Everest is 29,000 feet above sea level, the City of New average is about 33 feet above sea level. So when "aqua man" decends with the movvie herione to the Statue of Liberity and given that the "land" they found at the end of the movie was the last 500 to 600 feet of MT Everest the Statue would have been 28,000 feet underwater, (talk about dark and cold) or about 5 miles.

  6. Barotrauma is one of the most common dive-related injuries. Proper equalization is essential.
    I have small eustacean tunes and my ENT doctore reccommended nasal spray before diving and it really has helped!
    Nose drops such as Sofradex (NOT available in the US) can also help, but excercise *caution* once you begin to use it – you must continue for the remainder of your trip or else suffer a 'rebound' tightness due to its prednisone ingredient….
    Reverse squeeze upon ascent is no fun either..make certain your dental work is clean!

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