I woke up with a headache this morning. It hadn't gone away by noon, so I decided to take a nap. That didn't help either, so I took an Advil and a shower, which helped somewhat. After about another hour, I took another nap and felt better. I'm not happy about having to take so many naps, because I lost time that could have been put to other use (I was hoping to do some housecleaning), but I suppose I really needed to sleep. I'm not sure what caused this – it could have been the chlorine in the pool, or a drop in temperature last night that disturbed my sleep. I can remember chlorinated pools giving me headaches in the past, moving me to avoid them whenever possible. But perhaps part of the headache came from swimming underwater. Perhaps I'm not used to the change in pressure. Anyway, perhaps I'll try it again in a few days.