How can I repair a puncture in a PVC swimming pool?

My PVC swimming pool has 3 rings (top middle and bottom) and got punctured in the middle ring. The patch/es that came with it to fix any punctures are useless. They are self adhesive, but will not stick on permanently peeling off after a little while. I've tried searching the web for solutions, but to no avail.

How can I repair the approx 5mm hole in the side wall?

Any help would be greatly appreciated in this very warm weather...