Underwater photography is one of the most difficult forms of photography to practice and to achieve. It requires sophisticated and specialized equipment and knowledge of some advanced techniques to achieve perfection. The major challenge is low light, loss of color and contrast. But there is always photoshop to the rescue. You can always pull out contrast and detail from photos taken at ocean depth or under water.
You need correct exposure, accurate focus and tracking focus for moving subjects. Its a specialized art and the images are rare and vivid. Mostly people use traditional or digital camera with watertight casing but some professionals prefer special underwater cameras. You can rent the equipment from a nearby photography store. If you are a canon and nikon shooter, chances are that watertight casing will be available for rent at low rates. Try it out before buying it.
Above is a collection of rare, fresh and amazing underwater photographers taken by talented photographers all over the world.
Image credits in order of images
4.crimson swim by Fikrees Projects