A world at high pressure where our body is carried by our lungs...
Indeed, your lungs are a kind of integrated buoy within your body. If you fill in your lungs with air, your body floats. If you empty your lungs, your body sinks. This is certainly the first thing that your instructor will let you practise in 1 meter of water. You will discover the power of your lungs and you will understand that you can control by yourself your depth by simply adjusting the volume of air in your lungs. This is the key of scuba diving. This will also be the perfect opportunity for your instructor to adjust the lead weight that you may need. If you can't sink when you deflate your lungs, it means that you need more weight. If you can't float up when you inflate your lungs, it means that you have too much weight.
Now, comes the second very important point: The pressure. Water is 800 times heavier than the air. The 10.000 meters of air above our head gives us an atmospheric pressure of 1 bar (or 1 Kg/cm²). Underwater, the pressure increases of 1 bar every 10 m. We should keep this in mind because the pressure affects the volume of all air spaces within the diver: The ears, sinuses, lungs and the mask. While going down, the pressure increases and reduces the air volume. While going up, the pressure decreases and expands the air volume. It is good to remember the table below:
|0 m||1 bar||1|
|10 m||2 bar||1/2|
|20 m||3 bar||1/3|
|30 m||4 bar||1/4|
|40 m||5 bar||1/5|
While descending underwater, the water pressure will push on your eardrum. You need to equalize your ears regularly before feeling discomfort, in order to compensate the water pressure. Your instructor will explain you how to proceed. While going up, the air in your ears normally finds its way back to your nose. In case not, check with your instructor how to proceed. Keep in mind that diving is a fun sport. Never force. It's not normal to feel pain.
Normally, sinuses equalize by themselves except if you have a cold. This disturbs the free passage of the air in all the narrow channels between your nose and your sinuses. Note that this is also true for the narrow channels between your nose and your ears. So... Never dive with a cold.
While going down, the pressure will squeeze the mask on your face. You need to blow a bit of air through your nose into the mask in order to avoid this effect. Some divers never experience the mask squeeze because they naturally blow a bit of air through the nose while breathing out through the regulator. While going up, the too much air will go out on both sides. By the way, no need to tighten your mask. It's better to select the right mask which fit you well. Your instructor will show you how to do.
While descending, the water pressure doesn't compress your lungs because the regulator gives you air at the same pressure than the water pressure. That's great, but remember: Never hold your breath while ascending. You must let go out the air which expand in your lungs while going up. In case not, you'll damage your lungs. No need to remind you that your lungs are essential to your life.
The regulator allows you to breathe pressurized air. That means that all your body cells will absorb pressurized air through the blood circulation. You must always ascend very slowly to allow a soft transition of pressure for your body cells. The maximum speed is 10m/min. How to measure it underwater? Just make sure to stay well behind the bubbles that you blow while ascending. The small bubbles go up at a speed of 17m/min.
If you swim fast, you breathe much and you can't use your lungs to control your depth. So... Calm down. Diving is a lazy sport. More you are lazy, the more you can use your lungs to control your buoyancy. As you breathe less, your scuba tank will last longer. One more benefit: You'll make less noise of bubbles and you will see the fishes closer.
You must have a peaceful and respectful behavior toward the marine life. Don't run toward the marine life. This will scare them away or you risk to trigger a defensive reaction. A peaceful diver sees more things than a diver who runs everywhere.
Never dive with a cold.
Equalize regularly your air spaces while descending.
Never force. It's not normal to feel pain.
Swim slowly. Calm down. Diving is a lazy sport.
Always respect the marine life.
Never hold your breath while ascending.
Always ascend very slowly.
We communicate with hand signs. This is an open language. Feel free to use some instinctive signs of the daily life. You'll probably be understood. Of course, your instructor will teach you all the standard signs.
Deeper than 10m, your diving time gets limited and you need to know more about the decompression process. See 20m Diver. We invite you to test your knowledge and do a medical check. Then, your instructor will present you all the diving equipment and he will start teaching you the wetted part in shallow water where you can stand up. Once you'll finish the course, your instructor will give to you your IFDI 10m Diver certification. This certification allows you to dive till 10m always guided by an instructor.
IFDI focuses on the minimum information, goes straight to the point and avoids you a long reading of a book.
Of course, if you want to read more, your instructor may propose you the right book for your level.
IFDI displays very few images to allow an easy loading even in remote islands.
Edited in 2015. Updated in 2019.