How to find the whole in my ice rink liner?

So we set up our ice rink in our backyard again this year, it's our 4th year doing it. So this year, we set it up and started filling. At about 3 am. we noticed that there was a splotch of water underneath the liner on the ground, so we turned the water off. In the morning when it got light, we got in the ice rink, the ice wasn't even half an inch yet so we broken off pieces of it and slid them aside so they wouldn't cut into the liner, and we started looking for the hole in the liner. After about 30 minutes of searching we couldn't find it. So my question is, does anyone have any idea of how we could find the hole? Gluing it isn't a problem, because we have a special kind of glue, its just finding the hole thats the problem. Thanks, any help is appreciated.