underbelly is wet

I just got a 2000 forest rivers cherokee 37' travel trailer that I have some things I got fixed and working last night. I was aware when I bought it I had work to do but price was right. I noticed when I was under it last night the whole underbelly is like a thick rubber my old camper was more like a nylon than rubber and my neighbors fith wheel has like 4x8 panels that come out. But this is more like a one piece rubber. But If I push up on it it feels like there is water in it. I am not sure where or how it is getting in. the walls do not show any signs of water in them or anywere else. I am not sure if I should just drill some 3/16 drain holes thru out to let it drain everywhere. I just would like to hear what or were to look to locate were water is coming from.