Of course when you first go through certification, you are taught the #1 rule of scuba diving: never hold your breath.

As an example, when you practice regulator recovery (sweep and reach methods) you are supposed to breathe out a small stream of bubbles, even though you’ve lost your air source.

A question that dawned on me _after_ I was certified is: would it be dangerous to hold your breath when out of air or recovering your regulator as long as you don’t ascend? Or are there other dangers involved?

I wonder if it’s just a bad habit to never get into in case you are ascending without realizing it (even when out of air) or are there other reasons?

Thanks!

Another reason not to hold your breath when breathing off a SCUBA system is that when a wave passes over the depth you are at gets deeper. After the wave passes you are now at a shallower depth because there is less water over you, even if you don’t move. Since the air you drew in off the SCUBA system is pressurized to the last depth you were at, you run the risk of over expanding the little sacks in your lungs.

It is taught in SCUBA class to blow tiny bubbles in case you change your level in the water without knowing it, and or you panic and try to swim to the surface.