SCUBA-DIVING Self contained underwater breathing apparatus
Candidates breathe under water for the first time. Discover buoyancy, pressure, volume, density and many new things.
A body can float, sink or stay neutral. Air volume and pressure vary in deferent proportions and the deeper we go the denser air gets to be.
Salt water is dense. So sound travels 4 times faster. Body heat is 20 times more conductive and objects appear to be larger and closer.
Safe diving is our goal. We plan our dive then dive according to our plan. We always dive 2 by 2. Ascending at 18m/min is the speed limit. We engage in a safety stop after every dive at 5m for at least 3min. One cannot talk underwater unless through a full-face mask. Communication can also be achieved by signs or by writing on a plastic slate.
We breathe compressed air that is dry, clean and essentially made of O2 and N2. Pure O2 is toxic at depth. In the case of narcosis, shallower depth is the solution. If N2 depth and time limit are exceeded, decompression sickness results and can be treated at the hospital.
The golden rule is breath continuously and never holds your breath. Do not go at altitude directly after diving. Wait 6hrs at least before going to above 300m, and minimum 12hrs to fly, and it would be better that candidates have a mature attitude.