Making good UW pictures depends also on knowing and previsualizing the UW world

UW photography is dominated by two factors. First the hardware that you carry with you , camera, lenses, housing, strobes, just name it.  Second,  UW photographical issues, like strobe positioning, lighting techniques, composition. But equally important is developing a 'good  eye'  for the  UW environment. Ideally,  you should  already have  ‘previsualized'   that is, have in in your 'minds eye' the scenes  you want to catch with your camera. This is no spiritual hocus pocus but neuroscience. The human brain is a fantastic flexible organ that is capable of 'mental imagery': we can visualise objects or scenes that are actually  not present in our physical environment. A good eye will  also help you recognizing at a single glance the beauty of a special UW scene. 

Imaging the underwater sceneries in your minds eye is easier to accomplish  if you are familiar with the underwater sceneries.   The images are then already 'stacked'  in your visual memory,  so to speak.  A good way to help your minds eye is to make little sketches, for example a drop off with soft coral and the position of diver along the wall or  the position(s) ofthe shark you want you capture under water.  If your target is a living species you should  have an idea of  the behavior of  the species and  the best way  to approach it.  Never chase it,  but just observe, anticipate and wait for that very moment (=a match with that ideal image in your mind) to come!