I had a scuba instructor who used to sneek up behind and turn off our tank valves... in the pool. You dont do such things in the real world. Also, in the real

I had a scuba instructor who used to sneek up behind and turn off our tank valves... in the pool. You dont do such things in the real world. Also, in the real world, i would probably break out my smartphone. Short of an emp strike, it will still run on its own battery and can act either as a rough set of instruments or to phone the tower and declare an emergency.