From the apple store site: "Apple Watch has a water-resistance rating of IPX7"
7 being immersion up to 1 m for 30 minutes. In my book that counts as waterproof enough.
Yes Apple say not to immerse it, but that is covering themselves as the standard they state includes immersion.
I'm figuring that Apple at the very least has got to stand behind Tim Cook's statement that "he wears his Apple Watch constantly, 'even in the shower'".
...and I'm betting that the Apple Watch can indeed easily survive daily wearing in the shower - - I think Apple's just covering themselves for the yahoos who wear it scuba diving in Cancun.