An encounter like this happens once in the lifetime. It was a risky plan but worth a shot. A diver has to always have spare air. This is considered to be at least 50-100 bar. Without air you simply die underwater.
Every diver knows that the ascent rate from the bottom to the surface has to be slow.
Otherwise you may end up with ruptured lungs or the bends, or both. So, the trick was to very accurately judge the amount of air in the tank so as to have just enough to get 2-3 minutes on the way to the surface. My gauge was showing 20 bar. The footage I was getting was mindblowing. I took the gauge in my hand next to the camera viewfinder.