At 40 meters depth, the pressure is 5 bars and the air we breath is 5 times denser than at the surface. At such depth, you need to be perfectly calm in all your moves and in your breathing. Unless you have a particular interest to dive so deep, IFDI recommends not to dive so deeply. Furthermore, your diving computer will allow you a maximum of 9 minutes of dive without the need of mandatory decompression stop. The Nitrox may help you to stay a bit longer but watch out to the oxygen toxicity with the Nitrox. See the Nitrox course.
At such depth, the water is colder, even in tropical countries. Furthermore, your body cools down also through your lungs. At this depth, you may notice more that the air you breath is cold. This is the result of a higher quantity of air passing through the regulator for each breathing.
You expose yourself to a higher risk of nitrogen narcosis. At such depth, the partial pressure of nitrogen is 3,95 bars (79% of 5 bars). Divers who are not sensitive to the nitrogen narcosis are much more rare. More you dive often deeply, the less you are sensitive to the nitrogen narcosis. That explain why your instructor is fine while you have the narcosis.
In the previous courses, your instructor explained the need to pay attention to your buddy. At 40 meters depth, this attitude is more relevant than ever.
The statistics show that most of decompression sickness cases happen after a dive deeper than 30 meters depth.
To dive so deeply, you should do a first aid course as well as knowing how to rescue a diver.
This is more based on training sessions directly explained and shown by your instructor rather than on the knowledges that you could gather here. Rather than trying to remember a certain rescue protocol, you must use your brain in order for you to adapt to the situation. For example, a person (who doesn't know to swim) falls in water from a pontoon. No need to run till a life ring which is located far away if you can simply grab the person with your hand. Now, if this person is twice heavier than you, you should get the help of someone before giving your hand... As you can see through this example, many factors will affect the most efficient way to rescue someone.
First rule: Don't put your life at risk to rescue a person.
This may simply increase the amount of people in a threatening situation.
Second rule: Make sure that the diver breaths air and no water.
Third rule: Ensure that the diver has the buoyancy which fit the best to the situation.
Fourth rule: You must use your brain in order for you to adapt to the situation.
Your instructor will show you many common situations which may arise in scuba diving.
No, you are not a professional rescuer. You do your best and this is far better than doing nothing.
Just ask how you may help rather than interfering with the rescuer. If you're underwater, position yourself in the rescuer's field of vision in order to show that you are aware of the situation and that you're ready to help, if necessary. Inform the other divers of the group that there is a problem. It is time to stop watching the fishes in order to pay attention to the present situation. Safety first, fun later.
Going deeper than 40 meters is rarely worthy. Would you wish to become a diving guide? In the meantime, we invite you to test your knowledge and do a medical check. Once you'll finish the course, your instructor will give to you your IFDI 40m Diver certification. This certification allows you to dive till 40m guided or not 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 2021.