Does this smell like chloroform to you?
After swimming in a pool, I'm generally lethargic and sleepy for the rest of the day. I have a theory about this, and it's not that it uses all your major muscle groups, nor that it's an aerobic exercise with resistance - nopenope. My theory (completely baseless and with no evidence) is that the chlorine turns to chloroform on your skin and keeps you in an easily-kidnappable state.