The clock in the deep end

Last night I was mending a lane rope underwater, except the rope was a clock chain and every link was a minute I'd watched a particular swimmer take. When I surfaced the pool was empty and the clock on the wall was ticking backwards, not to reset, just to measure what was missing. I've been staring at the ceiling ever since, trying to decide if that's grief or just how you count time when nobody's in the water.