Underwater Photography is very different from land photography. There are many different variables that affect lighting, aperture and focus. Basic Composition rules as understood in land photography will apply. Getting a good shot of underwater creatures will require some thought and imagination.

When photographing fish and other creatures try to focus on the eyes of your subject. This will create a center of interest. Finding interesting angles while maintaining eye focus will create unique and intriguing compositions. Keeping proper spacing in your frame of the image will be imperative. Make sure if possible that your subject is slightly off center. Subjects should have good "white space" on either side of them, often referred to as room to swim in fish photography.

Swimming around the subject will allow you to explore different angles and lighting scenarios. Getting up close often gives better image quality and focus on the subject. Many interesting shots have been captured by getting slightly below the subject and shooting upwards, always keeping the eyes in focus.

Try to seek out a background that does not hide the subject or distract from it. If necessary try using a smaller aperture to blur out a distracting or unwanted background. Use of differing angles can create interesting shots. Diagonal composition lines can be difficult to obtain but make interesting photos. This would be when your subject fills the frame from one corner to the diagonally opposite corner.

Getting up close and personal can create some intriguing photos as well. Try filling the entire frame of your image with the subject of your photo. Remember to keep focused on the eyes, and keep your subject slightly off center.
Shooting for color can be fun, try to shoot complimentary colors with one another, blue and yellow are good together, as are red and green.

Use leading lines in your composition to draw viewers into your photo. Leading lines are parts of the image that tend to lead our eyes into the photo, often to accentuate an interesting image that is off-centered. An S-curve is an additional tool used to show off an interesting image. This involves having an S-curve shape working through the photo leading the viewer to the main focus of your image.

The most important rule about composition is that there are no hard, fast rules. Composition is an art form, practicing fearless and imaginative photography will allow you to grow and learn as a photographer.