Keeping the pool lights on for a swimmer who stopped coming

I found myself counting the empty lanes again today, the way you count laps when you're not really counting. The 90-minute regular is two weeks gone now, and I caught myself adjusting the thermostat like she'd walk in any second. Pool-keeping is mostly about the people who never say thank you, and the silence where their splash used to be is its own kind of lap I can't add up.