Please feel free to wear whatever meets your vision. One of my favorites is just simple white dress shirts and jeans. Hey, go barefoot too ! On the beach when you’re comfortable and relaxed it shows in your portraits. In addition, the white shirts don’t compete with the colors of the water and sun. I do suggest that you consider not wearing vibrant printed clothing, black, or navy blue. You most likely will be sitting in some images, so excessively short skirts, rompers, and shorts may not be flattering. At minimum you want to avoid any clothing that clashes, i.e., everyone in white with one person in orange (actually happened). As of late, some clients are using a watercolor pallet which is really nice and can be mix-matched. Mostly think light colored or white, not necessarily matching. Again, avoid dark colors like navy or black, except for pants/shorts/jeans.
If you wear eyeglasses with photochromic (Transition) lenses, you may want to consider not wearing them, but it’s up to you. In addition, a select few clear lenses are highly reflective and will refract/reflect incoming sunlight and hide your eyes. This is your responsibility to make a determination prior to your session, and is not correctable in post production.
Mark Block