All devices like this can handle a bit of water - most of them are rated to survive being submerged 1 metre for half an hour, which is more than enough for surviving a shower.
I shower with my smartwatch every single day, and I am sure the Apple Watch has no problems with something like that.
People aren't going to take off their watch to wash their hands. In any case, I'm sure Apple has ensured the product would not be damaged by minor water splashes.