At first glance it’s natural to assume this is a hotwife at play in the surf with her boyfriend given the smile on her and the erection on him, but if you look closer at the details, I believe it’s much more likely this is her cuckold husband and both are playing with her boyfriend as witness.
Notice how she’s moving away from him while keeping him from touching her as he intended. Both are looking in the same direction for the reaction of someone on the beach. The male is also fully shaved, something typical only in cuckolds and porn actors and he’s not a porn actor. This all leads me to believe this was a day at the beach for all three; perhaps it’s the beach where she first met her boyfriend.
Her boyfriend might be amused only watching them play now, but it will be the husband only watching themplay later.