Decompression Theory Made Simple: Why We Don’t Just Fly to the Surface

Dan Johnson
May 9
2 min read

If you’ve ever looked at your dive computer and wondered why it’s counting down those "NDL" minutes, you’ve encountered decompression theory. You don’t need a degree in hyperbaric medicine to understand it—you just need to understand how a bottle of soda works.

At Dream Team Divers, we believe that understanding the why behind the rules makes you a safer, more confident diver. Here is the "no-headache" guide to what happens to your body underwater.

Diver doing a Deco Stop on the line with a extra scuba tank in Pattaya, Thailand with Dream Team Divers

The "Soda Bottle" Analogy (Henry's Law)

Think of your body like a sealed bottle of sparkling water.

On the surface: The bottle is closed, and the gas (CO2 in soda, Nitrogen in your air tank) is under a specific pressure.
During the dive: As you descend, the pressure increases. According to Henry’s Law, as pressure goes up, more gas dissolves into the liquid (your blood and tissues).
The Ascent: When you start to go up, the pressure drops. If you open a soda bottle slowly, the gas escapes in tiny, invisible bubbles. If you "fly" to the surface and open the cap too fast? Calamity. The gas rushes out all at once, creating a fizzy mess.

In diving, that "fizzy mess" is what we call Decompression Sickness (DCS).

Tissues: The "Fast" and the "Slow"

Your body isn't just one big tank of water. It’s made of different tissues:

Fast Tissues: Your blood and lungs absorb and release nitrogen almost instantly.
Slow Tissues: Your fat, bones, and cartilage take a long time to soak up nitrogen, but they also take a long time to let it go.

Your dive computer is constantly running math in the background, simulating these different "compartments" to make sure none of them get too "full" of nitrogen.

NDL: The "No-Stop" Limit

Your No-Decompression Limit (NDL) is simply a timer telling you how much nitrogen you can soak up before you must perform a staged decompression stop on the way up. In recreational diving, we always stay within these limits so that we can technically swim directly to the surface in an emergency (though we never want to!).

Why We Do a Safety Stop

Even if you stay within your NDL, your body still needs a "breather." A 3-minute stop at 5 meters is like cracked the cap of that soda bottle just a tiny bit. it allows the "silent bubbles" (tiny bubbles that aren't harmful yet) to filter out through your lungs safely.

A diver ascending from a wreck dive using the line and doing a safety stop at 5 meters checking his computer in Samae San, Thailand with Dream Team Divers

3 Pro-Tips for "Cleaner" Decompression

Dive Nitrox: By reducing the amount of Nitrogen in your tank, you soak up less gas, giving you longer NDLs and a higher safety margin.
Stay Hydrated: Thick, dehydrated blood doesn't transport gas as efficiently. Drink water between every dive in the Pattaya heat!
The "Slow-Ex" Ascent: The last 10 meters are where the biggest pressure changes happen. Go slower than your smallest bubbles.

Master Your Dive Science

Want to see the math in action? Head over to our [Dive Hub] on dreamteamdivers.com. We’ve built custom Nitrox and MOD Calculators so you can plan your profiles like a pro before you ever hit the water.

Ready to level up? Ask us about the PADI Enriched Air (Nitrox) or Deep Diver specialties on your next trip!