Every 33 Feet Down, Another Atmosphere: How Ocean Pressure Builds

You are carrying the weight of the air right now: at sea level it presses on your body at 14.7 pounds per square inch. You do not feel it, because the fluids in your body push outward with the same force. Dive into the ocean, though, and even a few feet down you feel the difference in your ears.

Pisces V, a three-person submersible that can work at depths of up to 6,500 feet, lets scientists observe the deep sea under tremendous pressure. Credit: NOAA.

Hydrostatic pressure

The pressure you feel is hydrostatic pressure — the force per unit of area that a liquid exerts on an object. The deeper you go, the more water is pressing down on you. For every 33 feet (10.06 meters) of depth, the pressure increases by one atmosphere.

How whales handle it

Many sea animals have no trouble with high pressure. Whales cope with dramatic changes in pressure because their bodies are flexible:

• Bendable ribs. Their ribs are joined by loose, flexible cartilage, so the rib cage can collapse under pressures that would easily snap human bones.
• Collapsible lungs. A whale's lungs can also collapse safely under pressure instead of rupturing.

That flexibility lets sperm whales hunt giant squid at depths of 7,000 feet or more.

Sources

Based on "How does pressure change with ocean depth?" from NOAA's National Ocean Service, a work of the United States government in the public domain.