Split photos — also known as half and halfs or over-unders — are one of the most popular types of underwater photos, and for good reason. More than any other kind of photograph, they help tell the story of the connection between the underwater and topside worlds.
Scubadiving.com shares the following tips:
First, find compelling subjects above and below. Then, look for calm conditions with bright light and clear visibility (use a big glass dome!), and choose your point of focus. Finally, use a small aperture, a fast shutter speed and rapid fire.