Officially called “over-unders” or “split-shots”, these underwater photos are occur when the top half of the photo, and are often shot with a very wide fisheye lens. Photographers say that these shots work best in shallow water and calm water, especially during the early morning hours. Since the brightness in the top half will be greater than the underwater portion of the photo, strobes are used underwater to brighten up that area. To get really technical, graduated density and split filters are used to help reduce the difference in contrast between the sky and the underwater scene. Continue reading for more.