It looks easy enough to take a photo of a nice orange sea fan with a pleasing gradient of blue water behind. Those of you who are just starting out in your underwater photographic pursuits, you've probably realized it's not as easy as it looks. Sometimes for reasons you may not understand it comes out perfectly. That brightly colored colony of soft coral was illuminated flawlessly and the water column behind starts with a light blue at the top and gradually runs into a dark royal blue at the bottom of the frame. The following dive you're bursting with confidence because you're now a master underwater lighting. You leave your camera settings and strobes set up the same and start blasting away at the reef only to find out that everything coming back on your camera's screen sucks! The water is a less than pleasing slate-grey-blue and your gorgonian subject is the opposite of colorful. Stress and confusion take control as your artistic prowess begins a downward spiral at your inability to sort out this lighting quandary!

I Can See the Light!.

Understanding the light is quite simple really, as the sun comes up and moves in arc over the earth (actually we're the ones moving but we're not astrologists so let's just pretend were moving to keep in simple) the amount of light increases. No doy right? Well what also happens that you may not have noticed is that that the amount of light in the water changes significantly which has a big effect of the water color. On the morning or late afternoon dives there is less light in the water so you'll notice that the water is that idyllic deep dark blue. If you take a photo of a sea fan set against the blue water the bright orange of the fan will contrast beautifully against the dark blue of the water. As the sun rises higher on it's arc the light increases in the water column which changes the water from a dark blue to more monotone slate blue. Try to take the same photo the sea fan and it becomes a lot harder, or impossible to get that nice orange-blue contrast.

If it helps, think of it like shining a flashlight on land. If you shine a flashlight on your garden's rose bush around dawn or dusk, the roses really stand out against the rest of the dark garden. Shine the same light on them around one-o'clock in the afternoon and you will barely see a difference. Reason being, your flashlight/strobes have too much light to compete with. It is this reason why it's easier in the morning or evening evening, down deep, or on cloudy days, to get that well lit foreground subject with a dark blue background. This is not to say that you can't take nice colorful images on sunny afternoon dives, you'll just need to do a few do a few things differently.

Step One: Find your Blue

• The first thing to do is find that nice blue water. The best place to find that perfect blue is on a morning or late afternoon dive, before ten-o'clock in the morning or after three-thirty in the afternoon and generally anywhere from 12-20 meters. 
  
• How do we tell when it's just right? The basic idea is that you should be able to get a nice dark blue background without sacrificing your shutter-speed, aperture, or ISO too much.
  
• If your desired underwater camera setting is ISO 200, f8,1/125. You want to be able to get that nice blue with those settings, or as close to them as possible.
  
• Until you can read the light with your eyes, take some test shots with your desired settings of the water column until you find a gradient you are happy with. 
  
• Remember to keep a slightly upward angle and the sun just behind you. For now don't worry about sun-bursts. 

Step Two: Find your Subject

• Once you've found that depth where the light is just right, now you just need to find that perfect subject. 
  
• Finding the right subject is more than just finding a nice piece or coral.
  
• The best subjects will be aesthetically pleasing, a size that we can easily light up entirely with our strobes, a color that will contrast well with a blue background, and in a position where we can photograph it with the blue water behind rather than a cluttered and distracting reef or wall. 
  
• Once you find it, it's just a simple process of illuminating it with your strobes.
  

Step Three: Aim and Fire

• I like to start with my strobes on full power and then work my way down. Some photographers may say otherwise. 
  
• My logic is that if I have only a few seconds to compose and light a shot I would rather have too much artificial light than not enough. It's easier to correct too much light in post production than a shot with out enough light.
  
• Position your strobes accordingly, just behind the lens and angled out just slightly to reduce the amount of backscatter. 
  
• Compose your shot and fire, analyze your shot, and then fine tune your settings.  
  

It's All Wrong!

If all of your images are coming back dull, with water that is just not the right shades of blue despite the twenty meter vis, and your subject is just not as vibrant as you know it should be, there is still hope. The reason, MOST LIKELY, your images appear this way is due to the fact that there is just too much light in the water. But Alex, surely we can adjust the exposure to compensate for that? Of course we can, we can change our exposure settings to let less light in making the water a darker blue. However, if your subject has a width of a meter or more, you'll probably notice that your strobes will have a hard time exposing it correctly despite being set to full power on both strobes. But why Alex, why can't my stupidly expensive underwater lighting apparatuses light up that sea fan? Well, its just like the flashlight example. The sun is so powerful by mid day that we need to reduce the amount of light entering our camera considerably via shutter-speed & aperture & ISO to get a dark background, which in effect reduces our strobes overall effectiveness. If you want to illuminate a large sea fan on a bright day, you'll need to seriously strong strobes, or a full frame camera with a really wide lens to get you closer.

The Solution

One thing to do when there is just too much light to compete with is to look for a new, smaller subject. With a smaller subject we can bring the camera a lot closer without sacrificing composition, thereby reducing the distance our flash needs to travel and can deliver a more concentrated light. Another option is to look for areas of the reef where the sun doesn't reach, like overhangs or the undersides of bommies.