Turns out, the Apple Watch is pretty water-resistant—as long as you take care to clean it.
I suspect that the watch's water resistance has been undersold by Apple just like battery life: it's better to under-promise and over-deliver. Still, it's a personal decision on whether you want to ignore Apple's recommendation. You're not likely to get much sympathy at any subsequent trips to the Genius Bar.
He wrote a great piece on the Apple Watch's water resistance in the real world, chock full of interesting scientific bits about the Watch's aluminum, glass, and rubber construction; important tips about cleaning the casing, and his frustrations over capacitative touch.
I sent this over to my father almost immediately after I saw it—he's been doing daily swims and lamenting not being able to use his watch. I don't know if Hockenberry's article will convince my dad to change his mind and take the plunge, but it's a good read, nonetheless.