A sheer beach cover up dress is meant to be layered over a swimsuit so the opacity matters less than the drape. The sheer fabric shows the swimsuit underneath which is the point. The dress should be loose and easy to slip on and off. Knee length or longer gives you actual coverage. Light colors and simple patterns work best. The fabric needs to dry quickly since you will get salt water on it. Sheer cover ups are about ease and movement not about hiding anything. Pair with minimal jewelry and let the simplicity of the dress be the point. These dresses are practical and they photograph beautifully on vacation.