Thanks for your very interesting post, as it highlights to me how relevant it is to my own near-drowning when I was 19. I was in a large pool with a whole group of friends. Young macho guys as we were, we were dunking each other, playing wild games etc...doing what young guys do. At some point I decided to swim away from the group to attempt to swim the width of the pool underwater. Started in the deep end, swam all the way to the shallow end, about 50 yards i suppose, and felt OK enough to turn around without surfacing to swim back to the deep end where the other were.
Did not realize they did not know I had just spent about 1 minute underwater when they saw me appear underneath them. By then i was desperate for air, but pushed myself to reach the deep end bottom corner of the pool before surfacing. By now, I was starting to get that tingling feeling in my lungs from CO2 build-up and my abdomen started to contract as my body wanted to breathe. Finally reached my target and rushed to the surface while exhaling most of my air, ready to gasp for some fresh air once I would reach the surface...but as I surfaced and inhaled I got immediately pushed under by the other guys..who did not know I was already desperate for air. I started struggling a bit and after maybe 15 seconds they let me go but on the way up I could not stop myself from gasping for air and cold water went all the way down my windpipe into my lungs. Even though I got my head above water, and opened my mouth my body felt like stunned by that event and my throat locked-up. Then the other guys thought I had taken a good fresh breath and I got pushed under again. They used their arms and legs and pushed me all the way down to the bottom of the deep end. Strangely enough, I don't remember struggling much at all from then onwards. My body was so focused on the water intrusion and I started to cough, and then gaspo, but nothing went in, my airway just felt locked like I was choking (I suppose I was actually). My chest felt like as if it was spasming for maybe 20 seconds or so and then they let me go but it felt like as if my legs and arms were paralyzed, and all my focus was on trying to breathe. Finally my chest relaxed, and I managed to take some small breaths of water and I wanted to swim up but I saw the surface getting further away from me as I sank back to the bottom, very relaxed by now and actually feeling good as the water inside me seemed to make me feel relaxed. Everything went black as I saw someone swim down towards me. Came by as they were dragging me out. One of my friends took me to the doctor. felt really tired for a couple of hours and spent one night in observation at the hospital. Only thing I felt next day was sore muscles in my throat from violent coughing underwater, and had a minor lung infection, but was OK for the rest.
Anyway...very long story, but all my friends afterwards told me that I did not look like as if I was drowning, actually fairly calm and nothing alarming to them. I suppose the intense gasping and coughing I experienced during the drowning was not necessarily visible to the outsiders. And as people before me confirmed, once you take that first breath of water, you can't really yell out for help anymore, even if you get your head above water, and once you keep on drowning your body just redirects all available oxygen to your vital organs and your arms and legs become rather useless. From my own experience, drowning can be a very quiet killer.