Underwater Exploration: the Underwater Exploration Quiz Answer 1 University of Wisconsin Sea Grant
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1: How long will this person breathing through a super long snorkel be able to stay underwater?

Answer: Only as long as they can hold their breath; the force of pressure is so great at that depth that it is impossible to draw air down a tube against that pressure.

The pressure of the air around us is about 14.7 pounds per square inch. You don't even feel it, because you're so used to it. But water is much denser than air.

One way of seeing this is to release a bubble of air underwater -- the bubble races to the surface to a place where the pressure is lower. Underwater, pressure increases by "one atmosphere" (the equivalent of atmospheric pressure, or 14.7 lbs./sq.in.) for every 33 feet we descend into the water. This means, for example, that the pressure at 66 feet below the surface is 44.1 pounds per square inch, or three times that of the atmosphere.