I’ve actually been in this exact situation before! y family with my kids and everything were at the “family pool” at a resort where a mom next to us was in the tiniest thong bikini on the planet.  It was uncomfortable for my daughter in our situation, and then she started asking all the questions that night like “dad would you want to see me in that?” We didn’t say anything to the woman, it wasn’t our business to say anything.  I felt like if we were too uncomfortable we could just leave. But it does beg the question, should there be a dress code at family areas in swimming pools and beaches etc?