Most bathroom failures are invisible on day one. The tile looks perfect, the glass is spotless, and the problem is a shower pan that was never sloped correctly or a wall that was tiled over bare drywall. In South Florida humidity, those mistakes show up faster than anywhere else.
A correctly built shower starts with a sloped pre-pan, a continuous waterproofing membrane that turns up the walls and over the curb, and sealed corners, seams and niches. Only after that is tested does tile go on. Ask your contractor to name the waterproofing system they use and to show you the membrane before it is covered.
Large-format porcelain and marble-look slabs are popular in Boca and Delray bathrooms for good reason: fewer grout lines, easier cleaning and a calmer look. They also demand a flatter substrate and more careful layout, so the installer's prep work matters more, not less.
Ventilation is the other invisible detail. A fan sized for the room, ducted to the outside and run for twenty minutes after every shower does more to prevent mildew than any grout sealer. We size and duct it properly instead of just installing one.
Build the bathroom in the right order, with the right materials, and the beautiful part stays beautiful because it was done correctly underneath.