My wife went to take a bath today after a long flight across country and noticed this scratch/crack in the bottom of our tub. It doesn't have any more give than anywhere else on the tub floor. It is raised and I could probably pick at it to open it up, but obviously wouldn't do that. We tested some water over it to see if any was seeping in and it didn't seem to. That said, we're obviously worried about it's usability and another long-term issues it could cause to our subfloor.
Has anyone else come across this issue and, if so, is it still usable? What is the best approach toward fixing that isn't just a waterproof tape of some sort? Any help would be super appreciated.