Prolonged exposure to pool ingredients like chlorine can wear down lens coatings. If your sunglasses have an anti-reflective coating, they shouldn’t come with you in the pool.
Clothing is filled with dust and debris, as are beach towels and napkins. When you rub it against your glasses, you can unearth these small, abrasive materials and cause damage.
Cleaning your glasses routinely will ensure they always sparkle. Clean them as part of a routine that goes alongside your existing summer activities, like cleaning your bikinis.