Let me into a secret, almost all coating/paint companies are selling bathtub coatings are making all there coatings so cheap because a bathtub is considered a "water/moisture splash area" Not a submersion fixture.
What does this mean??? It means that the coating that these supposed coating companies are selling are only splash rated NOT submersible. In short it really means the coating is not meant to be underwater at all!
Now why would a coatings company that is making bathtub paint make a coating like this???
uhmmmmm, let me think... Maybe because they are trying to make as much profit as possible and if they keep selling there coating then who cares!
I only use submersible coatings.
The next time you consider a refinishing company to do anything with your bathtub or shower area consider asking them if there coating is really submersible, because you know it only makes sense to put a submersible water proof coating on your bathtub, but ask them anyways I bet they don't even really know!