Water leak, we cannot find.

We have been parked in the same site since January 5th of this year. We are winter Texans along the gulf coast. So the trailer hasn't moved and it really hasn't rained enough to talk about all winter. The shower is located above the trailer basement so if that is the location of the leak I'd think the basement would be wet, but there is no water in the basement. This leak seems to be below the basement, granted there really isn't anything below the basement other than that plastic membrane. So all I really know is that the leak is very low in the trailer. We will be heading for home in about two weeks so we have decided to cut a hole in the membrane at the lowest point and just head for home. If it leaks along the way all the water will be able to escape out the hole. Once we get home we'll take the trailer to the dealer where we bought it and let them find the leak and fix it. When I first noticed the badly sagging plastic membrane hanging down so low and obviously filled with many gallons of water I panicked a bit, but with the help of ya'll and thinking it all through I've calmed down and we'll be fine going home. Thanks for your help.