Sunglasses are a "must", even in winter!  They protect your lens, retina, cornea, iris, the white of the eye and the skin around the eye.   When shopping for new shades, be sure they have 100% UV protection.  Polarized lenses don’t add extra UV protection, but they do reduce sun glare which is especially great for people who love to be by the water.  Colour and lens darkness is up to personal preference; some colours can even help enhance vision for particular sports and activities.  As with any pair of glasses, quality lenses make a difference for both durability as well as optics by limiting distortion, thereby enhancing clarity.  A good frame is also important, with large and/or wraparound styles providing additional protection from the sun.  To learn more, check out this article.