After 2 weeks of ordeal (hard training), my oldest and I have successfully passed the level N3 exam for autonomous diver up to 60m depths.
One part (I'd rather call it rite of passage) was to go down between 10/20 m, make sure you where balanced and trimmed correctly, then take off your diving fins, remove your jacket and finally your diving mask and regulator to go on a little swim through 10m. Come back to your equipment stock, put the mask back on and empty it from remaining water, then only take back the regulator.
Other exercise were to make an assisted ascent without diving mask from 20m, plenty of other assisted ascents from 20m and 40m depth, deploying the shutes from 30m, etc.
It was quite sports, especially since we had changed some of our equipment. But by remaining calm, it worked.
After discussing it with the instructors (we had 4), it was actually to test our mental ability to deal with difficulties in high depth and make sure that we did not panic. So - all in all - we passed and got our Diving N3 certification.
Congratulations to my Oldest who passed with flying colors!