I agree with the advice to speak to a tube expert about it ... but I had to remove and reglue a patch on mine a couple of months ago, because it was peeling off due to improper preparation. Unfortunately the improper prep was on the patch side so all the glue stayed on the tube....
I just peeled the patch back slowly and carefully (the problem was that it was starting to lift at one end and the water driving into the gap was opening it up). To be honest I think you'd have to pull pretty hard to tear hypalon, I did some "abuse testing" on the old patch with pliers and a vice after I got it off, and it is very tough stuff which is hard to tear unless something sharp has run across it first! If you manage to tear the seam (i.e. open it up more), my thought would be that it was probably a weakness waiting to let you down anyway so just as well to find it in the workshop not in the water?
After getting the patch off I used a flap wheel on an electric drill and just slowly but surely worked along the glue from one end, the glue sort of half-melts under the onslaught from the flap wheel and "peels back" ever so slowly without any adverse effect on the hypalon, it just comes up a nice orange colour
and it was perfectly prepared for gluing. No problems with it coming off now, and I had a good pick at it after a week or so once it was properly set.
It is hard work though - I flattened two batteries on the electric drill doing a patch that was only about 6 inches by 4!
If it is a seam then none of this may apply - I hope I never have seam problems on mine as I am not sure where to start either!
