Will my boyfriends penis shrink in a pool sorry for asking lol i just need the question answered ?

No ...: While soaking / swimming in the pool, one usually has no sexual arousal especially in the water below body temperature and the penis will shrink to adapt to its environment in a widely variable degree among men. So, the penis looks much smaller than its usual size; that's normal, but it will return to its normal size soon returning to a warmer environment.