General note before getting into the Apple Watch:
No watch, not even a diver's watch, is "waterproof" in the sense that it can be taken to any depth of the ocean, no matter how abysmal, and remain intact, keeping out the water however there are certain standard degrees of water resistance. No watch is marketed as waterproof as far as I know; watches are marketed as water-resistant at the lowest level, and water resistant to XYZ depth for higher levels.
What is the overall outlook regarding swimming and the Apple Watch?
Best Answer
We really don't know what Apple has in store for the Apple Watch as far as waterproofing it. YouTube is full of guys who test their Apple Watch to see if is waterproof, they take it down to depths of ten feet and lower for a pretty long time and, though not very useful while underwater (due to pressure, the touch screen won't work also the heart rate sensor isn't always accurate), I've yet to see where the Apple Watch doesn't survive being taken underwater.
I've never submerged my Apple Watch Sport, but it has gotten wet quite a few times and I've rinsed it off in the sink many times, too.
Given that the Apple Watch is almost waterproof today, I think that Apple just doesn't want to call it that for fear that they will have to replace any units that break when taken deep underwater.