If this is just a bezel insert then it is not beyond any one, but firstly does it fit in the recess in the bezel its self, a perfect fitting one should just snap in place and remain there with out glue. (is there any glue still stuck in the bezel if so remove it with a pin or screw driver, it should just scrape out) If the bezel fits in the recess but is loose then it requires gluing, i have used clear nail varnish for this in the past when i had a nice flush fit, i have also used super glue i found the nail varnish to be better to remove at a later day when i replaced it after some other work. If how ever it is too big that is where it starts getting a bit tricky as it needs to be filed down but equally all the way round until it does fit, it may also need thinning down in hight as well.. A for water resistance i have found all my sports watches to be able to resist a shower at least just by checking the back is on tight (put on some rubber kitchen gloves and tighten with your thumbs) and the crown is screwed down. On the bezel insert just be careful with the alignment.