Reflected UV not as big as we thought
We have always been led to believe the UV radiation reflected off the water and sand when at the beach, or out on the water is part of the reason we are more prone to sunburn when undertaking these activities.
Interestingly, a recent study in the medical journal Photodermatology Photoimmunology Photomedicine (March 2018) concluded that in fact the vast majority of the sun's UV radiation passes into the water, and very little is reflected especially when the sun is high in the sky (the time when the UV level peaks). We certainly notice the reflected light with our eyes, but the reflected UV does not appear to have a major bearing on our skin.
The corollary of this fact is of course that we are still exposed to almost the same UV when we are swimming under the water as when sitting on the beach. The UV index was only reduced to half by a depth of two meters under the surface.
Adequate shade and protection from the sun above remains the priority when enjoying the beach or water sports.