Went and bought a snake and came back and snaked the drain. At first it didn't seem to do anything then it started to slowly drain. After running it back and forth it seems to be draining faster now. I'm going to give it a few more back and forth and see how that does. It must have been some kind of plastic seal maybe between the tank and the line? I mean it held the water in the shower overnight so it had to be sealed somehow and the snake didn't seem to make contact with anything solid.