Since the original announcement of Watch, Apple made it clear that it is tough but not waterproof. However, with the product in the hands of users, it soon proved that it can handle much more than the company promises. They even did swimming tests with him and there was absolutely no problem.
That said, the developer Ted Bradley ported an app originally created for Pebble and shows in the video below filmed at the London Aquatics Center, in London (England) how it works well on the Apple Watch:
As you can see, the app is cool and even integrates with Sade (Health). It is not perfect because the data itself is updated in the interface only with the screen on, that is, as soon as you look at the Watch it initially appears “out of date” (a few seconds).
Despite this, Bradley may not even be able to submit the app for Apple's approval as there is a rule in the App Store that goes against the fact that Watch is not officially waterproof. Unfortunately we will have to wait for the second generation of the watch to be launched, hoping that it will be certified by Apple for use in swimming pools.
Personally, I think this is one of the major flaws of the Apple Watch. My Activity History (Activity) is extremely affected by the fact that I cannot register my exercises three times a week (Monday, Wednesday and Friday the days I swim). A feather.