I have the tile up in the bathroom and there was water damage by the corner of the tub and I don't know if I need to pull out the tub? I have some pictures and was able to get underneath the floor as well.Attachment 45955Attachment 45956

Unless the floor is bad, just lay a new piece of wood, pressure treat into the wall cavity and put the drywall back. You will have durock or similar on the floor before tiling?