An embolism can occur in 3-4 feet of water. If your instructor neglected to pass this little tidbit on he screwed up big time. Just how long have you been certified and thru what agency? Breathing compressed air is nothing like breathing thru a snorkel. If you'd been properly trained you'd know this. Even at 3 feet you are taking in more air than you would at the surface. Don't exhale and the lung may not expand enough to account for that. Result- somebody hurt bad or dead. There's also a reason that we are not allowed to train below a certain age. For PADI 8 yr olds but they never go under the water. they are on surface breathing thru a reg with a float vest on and only the face in the water. 10 yr olds can dive- with a DM, AI, Instructor or parent. In the Y program 12 is the minimum. There are reasons for these rules. Are you an instructor? Do you know how to train kids to breath on scuba? Obviously not since you don't seem to realize what dive tables are for and not for. THis has nothing to do with tables- It's basic dive physics and physiology. Guess you missed that lecture or your instructor did not think it important.
You also seem to know nothing about your spare air. If it will deliver air at 60 feet it does indeed pressurize your lungs. WHAT KIND OF TRAINING DID YOU GET AND FROM WHO? Cause they were a dangerous individual based on the complete lack of knowledge and understanding regarding just what this sport involves. My God! I can't believe some of this. I do hope that this is a troll. If not, a tragedy is in the making at some point.