Be honest. Did you think we'd accidentally uploaded a picture of a naked woman swimming until you scrolled down and saw the fins? This is not a woman in the water. It's also not Ariel from The Little Mermaid, or photo trickery. It's a picture of a Beluga whale swimming towards the surface of the sea.
In days gone by, sailors stuck on boats crossing the ocean for weeks or months on end reported sightings of mermaids; mythical creatures which were part woman and part fish. It's highly likely they were actually seeing part of these unusual creatures in the water. Beluga whales have taken a different evolutionary path to most of their kind; they're almost white in color, and as you can see here, their bone structure resembles a pair of human legs if you look at it from the right angle.