If 3rd party companies can waterproof an iPod Shuffle (I see swimmers with them attached to their heads all the time at the pool) I'm sure there'll be companies that can waterproof this watch.
I'll be damned if Apple restricts me from wearing this swimming.
Apple is not restricting you from doing anything with the watch. They will however decline to honor the warranty if you violate the terms of it.
I also thought the ability to waterproof the shuffle would translate to the Watch, but I don't think it will for the same reason that the waterproof nano never worked, the same company that waterproofs the shuffles withdrew it almost as quickly as they offered it due to the numerous failures. There's a lot of factors besides water ingress that submersion and force may affect. The Shuffle is basically encasing the entire electronics in a waterproof coating, like a paperweight. But adding a backlight, and taptic engine, etc may not function properly encased like that. I suspect the Digital Crown would be a major impediment to water proofing the watch that way.
If you insist on taking it into the water, then you should get a waterproof case for it. Third party swimming apps will most likely hit the App store with the intention of being used with such a case.
But make no mistake, the watch is evidently more water-resistant than IPX7 suggests, but moving water and resulting pressure (like from a swimming stroke), is likely well beyond the scope of what the watch can routinely endure. Keep in mind too that temperature changes can also affect the seals as well. Going from a 90 degree afternoon in Santa Monica into a 60 degree ocean is enough to cause those seals to quickly contract, combined with outside force, leading to water ingress. Likewise going from a 50 degree atmosphere into a 103 degree hot tub.
Apple says not to use compressed air to clean the watch -- gental flow of household tap water from a faucet for no more than :10 was recommended by Apple. That's a far cry from splashing about in a pool, or submerging in dramatically different temperatures.