Well, with all the crazy dives I did for Cousteau, never an issue but more recently, in 2014, when I visited Classroom Under The Sea I did run out of air. Here is an excerpt. For more you can check out my longer blog entry titled "Back to the Past" @ http://frogmenbook.tumblr.com
This was in shallow water but frankly quite scary, since I was stuck...
"Best laid plans…we headed toward the corner of the habitat and the common room window for Jess to take the photo. Rather Bruce did. My tank’s cylinder valve became tangled in a line that anchored the habitat. I quickly unhooked and hustled after Bruce but was surprisingly short of breath. Something was wrong. Although I had no air gauge, I knew I was out of air. I had no choice but to surface.
I was concerned that Bruce would be worried. He could not surface or he’d lose the record..
I made my way to the diving dock. We confirmed a leak in the tank. - Megan said, “oh and by the way your nose is bleeding”.
Shame on me for not checking the air before the dive. I “assumed” that since I’d had 2,200 psi before the prior day’s descent, that I still had a mostly full tank. Overnight it had leaked."