Seems safe to shower with the watch. I don't know if I will....but if I do, I want to make sure that it would be covered. One day running and it starts to rain and then find out that Apple wouldn't cover it would be annoying.
I have also banged my watch on a metal stair well going around corners too quickly.
So yes for AppleCare + for me. Well yes as long as it is reasonable. $49-$79 sounds reasonable for the Sport model and $79-$99 for the SS.
I fully intent to shower with mine, and if it stops working due to water damage AC+ is that extra "insurance"