My first theory presentation today

As mentioned, I was not diving today, but instead I prepared my first theory presentation. As a Dive Con, you can teach students in theoretical subjects, spanning from Masks, over Dive Tables to Decompression sickness. So, today I was doing a 15 minute presentation of the "Regulator" (the thing you breathe from under water and where you can see your remaining air etc, see e.g. link here). The presentation was for my Dive Con colleagues and for several instructors. Today was my 'test' presentation. I did 'ok', but later on, I will need to get good enough grades and pass for at least 2 more presentations. Next subject that I need to present will be on Lung Expansion Injuries (typically caused by holding your breath when ascending; this can expand the air in your lungs to a factor 2 or more, which obviously is not good for the lungs :-).