Water Resistance after Repair

Depends on what instructions you follow.

Watchmaking is its own category of engineering and it came with its own ways of making/testing things. However wearable electronics are not watches so only part of these methods apply.

The most significant difference is that Apple Watch uses glued-on crystals instead of press-fit or screwed-on ones. It’s tricky to remove the crystal and clean the contact surface of adhesive residue, making new ones difficult to adhere properly even with all original parts and instructions.

And that’s IF you get original parts. Parts like the adhesive gaskets are critical to sealing performance and Apple don’t sell them publicly. Pretty much all of them are aftermarket alternatives, which probably don’t have the perfect composition and dimensions to ensure a reliable seal.

Then there is the testing part. The watchmaking industry uses an electronic pressure tester to either look for tiny deformations of the case during the pressure cycle, or use a manual pressure tester that pumps the chamber with air when the watch is dry, then immerse the watch into the water and vent the pressure and see if air leaks out of the watch, which proves that air leaked into the watch during the pressurization phase.

Such instrument does not work with wearable electronics. Apple Watch has speakers and water resistant air vents that throws these detection mechanisms off so the tests won’t work properly. It could even cause more damage by pumping the watch case with too much air and pop the crystal off when venting. All you can do is do a shower test and guess it may have worked.

So no, it can’t be done yet because proper instructions do not exist at the moment.