Hi, my name is Jonathan from Private Dive Service. In this blog, I want to go over Open Water Dive Manual tips, so keep reading.
Understanding Pressure When Scuba Diving
When we go scuba diving, we go under the water, which means we now have an increase of pressure around us. Why? Because we're suddenly surrounded by water, which also weighs something and puts pressure on top of us. We still have the surface air pressure on us as well, and that's very important to understand.
For every 10 meters that you go under the water, the pressure increases by one bar. So at 10 meters of depth you have one bar of pressure from the water, plus one bar from the surface air pressure — two bars total at 10 meters. At 20 meters it's three bars, at 30 meters four bars, at 40 meters five bars.
Understanding Volume and Density Changes
Besides increasing pressure when we go deeper, we also affect volume and density. Imagine you fully inflate a balloon at the surface and tie a knot in it. Air is made of molecules, so it is something. As we take that balloon underwater, the water surrounds it and puts pressure on all sides. The deeper we go, the more it gets squeezed.
At 10 meters we have two bars of pressure, so the balloon gets squeezed to half its size — the volume becomes half. The air doesn't escape; the molecules get squeezed closer together, so the density inside increases. When descending, volume decreases and density increases, always related to the pressure you're under. At 30 meters (four bars) the balloon is one-fourth of its volume; at 40 meters, one-fifth.
Equalizing Air Spaces in Your Body
Going under the water means we have to equalize the air spaces inside our body. Where are these air spaces? We have sinuses behind our face, connected by the eustachian tubes to our ears and eardrums. We also have the biggest air space, our lungs, and a little air between our face and mask. For now, let's focus on the ears, because that's where you feel the pressure first.
As you descend, water flows into your ear canal and starts pressing on the eardrum, bending it slightly. This isn't bad and you might not feel it yet. But if you keep going down without equalizing, it becomes uncomfortable and eventually the eardrum could be damaged. Don't worry — it's very easy to solve by equalizing.
Techniques for Equalizing Your Ears
To equalize, we create the same pressure inside as outside. The most common method is the Valsalva maneuver: pinch your nose, close your mouth, and gently breathe out. The air is pushed to your eustachian tubes and eardrum. This must be gentle — doing it hard can damage something else. Do it as often as you can, all the way down.
If that doesn't work, try wiggling your jaw and moving your head from side to side. If you feel congestion, blow your nose before you dive, and never dive with a cold. Many people have trouble equalizing at first — it's perfectly normal, and it gets better over time as you learn to feel exactly when to equalize.
Equalize early and often on the way down. If you feel pain, stop immediately, signal your buddy, and ascend slightly and slowly until you can equalize again. Never, ever force it. When in doubt, ask your instructor or a dive physician.