I'm thinking it would have to cover the sensors on the bottom to create a reliable seal, plus it would likely need its own band that attaches to the case. Not sure if the digital crown could remain fully functional, but the buttons should work. The touch screen should work, but probably not force touch. Maybe a transparent bottom to allow the sensors to work? Otherwise I suspect Apple wouldn't officially license it. For waterproof applications, I can't imagine the loss of either would be that major, especially if you're wearing the watch someplace where you're not going to be getting notifications you have to scroll through. I'd think you could work around force touch ... A few things might take a few more steps than usual, assuming you even need them. But I just did a search and don't really see anything for this yet.