LOL this is exactly what happened to me. I was at a pool with the gradual slope into the deep-end and I fuckedaroundandfoundout and drifted down the slope. It's probably my most vivid memory. I tried screaming for the life guard but like you I couldn't physically make sounds or vocalize. I somehow managed to dogpaddle to the ledge, right under the life guard, but she was zoned out and wearing some sombrero hat with large bug-eyed sunglasses. At that point I just gave up and lost my grip on the ledge and drifted back into the deep end and sank. I got to the point in drowning process where you're not afraid or panicking and you start to feel this sudden tranquility. My idiot parents (they were young) managed to fish me out of the deep end before I went to the other side and for some odd reason the pool gave me a little basketball (1980s)...I taught both my kids how to swim by just getting them comfortable in the water and teaching them how to kick. Teaching them how to ride bikes was honestly more challenging.