Breathing underwater in a slippery Pool

"I fell off the edge of a slippery tile pool while trying to catch a floating house key, sinking straight down to the dark bottom. At first my chest went totally tight and I held my breath expecting to choke on the water, but then I exhaled and took a small, hesitant breath in through my nose just to see what would happen. The water tasted cool and sweet, like fresh mountain air, and it filled my lungs without any burning at all. I just floated there in the quiet blue light watching tiny bubbles bubble up toward the surface, this huge, heavy wave of calm settling over my whole body. I realized I didn't need to push myself back up to the surface at all. Then suddenly I was standing in a brightly lit laundromat folding a stack of warm towels, but my skin still felt cool and refreshed, and that deep, silent stillness in my chest remained like I'd been resting for hours."