Original post by: f_andy_hershcovitz ,
I’ve done that by cleaning the old seal tape, and pasting RTV around the transparent cover frame, then carefully closed and tighten them overnight with laundry hanging clips. I didn’t try to soak it in water, to test if realy watertight sealed, but the seal look tight, and RTV is used for aquariums. so believe it will withstand some water. The drawback of this, that unlike the original tape that was designed to open the watch (and phones) by heating them with hot air gun, the RTV is also heat resistant, so opening it again for any reason could be nearly impossible (altough I believe that using a knife, carefully the cover can be pried again).