SR,
I found most of the underwater adhesives curled the vinyl patch way before I was able to get it to the bottom. One adhesive, Boxer-100 I believe, is a slow setting stuff that worked great. Available at pool stores. I'll have to take some pics of the rig to really clarify how I did it but basically I used a 3" paint roller taped to the end of a 10' PVC pipe and a paper clip arrangement and some plastic sheeting to hold the patch on the roller until I got it where I wanted it, then released it. As I said, tough to describe in words without pics. I'll try and take some tomorrow and post with a better description.
Al