Water doesn't crush you because the pressure inside your body generally equalizes with the pressure outside your body.
Here's a more detailed explanation:
Understanding Pressure
Pressure is the force exerted per unit area. In the case of water, the deeper you go, the more water is above you, and therefore the greater the pressure. This is because gravity is pulling down on all that water.
Equalization of Pressure
The human body is mostly water. Since liquids are generally incompressible, the water inside your body can't be squeezed much more tightly. Crucially, the pressure inside your body pushes outward with roughly the same force as the water pressure pushes inward.
The Real Danger: Air Spaces
The real problem at depth isn't the water itself crushing you directly. It's the air-filled spaces within your body, such as your lungs and sinuses, that are vulnerable. Increased water pressure can compress these air pockets. If these spaces are compressed too much, it can cause serious damage.
Here's a breakdown:
- Lungs: As you descend, the air in your lungs is compressed. Without equalization (e.g., through scuba diving techniques like exhaling), your lungs could collapse.
- Sinuses and Ears: Similar to the lungs, the air in your sinuses and ears needs to be equalized with the external pressure, typically by pinching your nose and blowing gently to open your Eustachian tubes.
How Deep-Sea Creatures Survive
Animals that live in the deep ocean have adapted to the immense pressure. A key adaptation is the lack of air pockets. Their bodies are primarily composed of water and other fluids, allowing them to maintain equilibrium with the surrounding pressure. Their cellular structure and biochemical processes are also adapted to function under high pressure.
For example, many deep-sea fish have:
- No swim bladders: Swim bladders are air-filled sacs used for buoyancy. Deep-sea fish generally lack these to avoid the problems associated with air compression.
- Flexible skeletons: This allows for a certain degree of compression without injury.
- Specialized proteins and enzymes: These proteins and enzymes function optimally at high pressures.
Examples
- Scuba Diving: Divers use specialized equipment to regulate the air pressure they breathe, allowing them to equalize the pressure within their lungs and other air spaces.
- Submarines: Submarines are designed to withstand extreme pressure. The pressure inside is maintained at a level comfortable for the occupants.
In Summary
The key is pressure equalization. Water itself doesn't "crush" you if the internal pressure of your body matches the external pressure. The danger arises from unequal pressure on air-filled cavities within your body. Deep-sea creatures avoid this problem through various adaptations, including the absence of air pockets and specialized biochemical adaptations.
