To create any good picture, you must know your subject to be able to capture its essence. This concept becomes paramount when shooting in the underwater realm. What creatures should you approach? Are they dangerous or not? Understanding the behavior of fish will enable you to produce stunning imagery. Study swim patterns and other details. How is the school of fish moving and how can you get near it? What is the position of a sharks pectoral fins, and is it aggressive or not? How long will it take for the manatee to come up for air again.Color is lost the deeper you dive reds, for instance, are the the first to go. Knowing the true colors of sponges and other marine life will help you compose better and more interesting pictures. These days, most of this information can be found on the Internet, where pictures of sea creatures abound.