Swimming Against the Tide

I dropped my son off at 5:20 am at the high school, for his off-season football weightlifting/conditioning session. The pool is not even open to the public yet, but within 5 minutes, I am able get into the locker room. I swim 2 warmup laps, and then I swim the same workout I did last week. I time my second set of 9 laps, and it takes me 10:15. It’s weird. I will be swimming a 2 fast lengths, and it takes me 57 seconds. Then I swim 1 fast and 1 easy, and it’s only 1:03. So, my fast laps just feel harder, faster –not so much.