We recently moved into a house that had an inground pool with it (later found out pool was built in the 70's). The home inspector was worthless and wouldn't look at the pool but I've had nothing but issues with it and now it is leaking.. Local pool shops all tell me the pool is concrete but after I dug down to replace the return valve i found it wasn't concrete but I have no idea what it is.. 1) the walls are separate sections with a caulking in between each panel 2) there's multiple areas where the coping is separating and when you look to the top of the walls it looks like the walls might be plywood.. Anyone have any idea on how to tell the difference between plywood walls opposed to fiberglass walls? Any information will help and be greatly appreciated so I can try and get everything fixed up as quick as possible