"Coordinate clothes" for the beach means to choose and match outfits that go well together in terms of style, color, and practicality for a beach setting. This could include selecting swimwear, cover-ups, hats, sunglasses, and sandals that complement each other. For example, you might pair a vibrant swimsuit with a light cover-up, a straw hat, and sandals in matching tones for a coordinated beach look.