Underwater photography is one of the most difficult photography techniques. Not only you need special equipment for it, but your must also be a good diver, with a lot of experience, able to approach to the subject you would like to capture to appropriate distance. Underwater all the principles of the standard “air-based” photography are turned around. Water has all the different physical characteristics for the visible light and therefore you need to consider this when taking photos underwater.
Different color of the visible spectrum of the light are absorbed differently in the water. And because mostly the cameras are made for standard photography, you need to manually calibrate the colors of your photos. In the graph on the right you can see how deep different color of the spectrum can penetrate. If you are diving on more than 7 m, there is no more red light and therefore you will need additional source of the light (flash).
Usually the beginners are trying to picture the subject from the distance. It’s a mistake, because often the water it not clean and the pictures consequently are not contrast and vivid. To solve this problem try to approach as much as you can to your subject. Additionally you can boost the contrast in Photoshop, but it’s always better to have good pictures right away, before the post-processing!
In the water is very difficult to get sharp photos of the subject. There is a lot dependent on your equipment, but there is also something you can do on your own. If you are not using the flash, try to increase the ISO speed of your camera. It is true that you may suffer some noise on the images, but this is much better than blurred photos of the underwater wildlife.
Another important reason why you need to get as close as you can when you are shooting with a flash is the back-scattering of the light in the water. Water is much more optically dense than the air, which means that the light is more quickly absorbed or scattered than in the air. Therefore the light passing through the water will reflect significant part of the ray back to your lens, before hitting the subject. This will be shown as the light overlay over your image and lack of contrasts and color in your photos. To avoid this: do not use flash if possible, capture in clean water and get near as much as you can to your target.
Nevertheless, some rules can also be derived from standard photography. For example, try to rotate sometimes your camera to the vertical position, specially when capturing the “fist portraits”. Also have in mind to take care of the background in your picture. Very well known photographer I have spoken to once said, that the background makes the picture beautiful and interesting, not the main subject.
Have all the listed rules in mind when capturing the wonderful underwater world and I am sure you will get the best from your diving. And do not give up if you come back to the beach and see on the camera not what you expected. Try to find out what was the reason for the bad photos and improve this the next time you go to the water with your camera!