How to fix small holes/separation in caulk around bathtub?
One more thing is to keep water in the tub when you caulk until the caulk dries. It's a pain to work this way, but flex in the floor under the tub when there's weight in it can help open up a gap in the caulk over time if it was caulked with no weight in the tub. Given that your caulk is doing a critical job it shouldn't have to do means you don't want to miss a trick. You definitely do not want water getting behind or under the tub. It creates a superb natural habitat for mold and rot. Long term, it would be best to install a tub surround (or equivalent) that correctly overlaps the lip of the tub.