Must be a reflection certainly not the moon this photo was taken a few minutes after the first one lo9king down onto Kotor bay
It's lens flare, John is correct re reflection but it's presumably not taken through glass or plastic so it's internal reflections in the camera lens. Another point is that it's basically impossible to have the moon and sun at that angular separation in any photograph, at that angular separation we are looking at the side of the moon in shadow, the opposite side of the moon which we can't see would be in broad daylight, and due to atmospheric scattering there would be zero chance of seeing even a sliver of the daylight surface of the moon because of the difference in illumination level, you can't stare at the sun and neither can a camera. edit: the only exception is total lunar eclipse or a partial lunar eclipse but the moon is not illuminated under those condition so what you see is the side in shadow and in both total and partial cases the moon vanishes the moment the eclipse is fully over because of the overwhelming brightness of the sun.
Looking down onto Kotor and Kotor bay from the descent in the Kotor cable car, the white shimees are reflection off the glass
