Photo Tips for Blackwater Diving

Are you the kind of person who will end each dive with a biology lesson?  Do you pride yourself on knowing everything you can about the natural underwater world? Do you read dive travel blogs? So tell me, hotshot, what do you know about perhaps the most common animal on earth: thaliaceans?

For starters, they are probably the most efficient animals that we know of. They pump water through a barrel-shaped body using very little energy and filter out plankton to feed. Thaliaceans can also reproduce and grow faster than any other multicellular animal and can be so thick that they clog up nuclear power plants. That’s because they lead two lives; a communal asexual phase where they reproduce very quickly through a process called selfing, and a sexual one where, well, you get the picture.  You might know them as salps or sea squirts and they are just one of the animals you will become intimately familiar with on a blackwater dive.

Blackwater diving is a special kind of night dive where participants are taken miles offshore over deep oceanic water. Weighted downlines are then tied to the boat.  Each diver is then attached to the downline via a shorter tagline.  These harness systems ensure that divers can’t wander too far from the boat, because if you find the bottom in 3000 feet of seawater, something has gone terribly wrong. 

The key to finding pelagic subjects like the pelagic nudibranch (Phylliroe bucephala) is to look small.

Clear photographs of salps and other gelatinous plankton can be tricky. They are always on the move, they don’t contrast against the background and finding the right camera settings can be tricky, but once you are all dialed in, making breathtaking photographs of a huge variety of body plans can be like shooting fish in a barrel.  Photo contest macro winners are frequently made on blackwater dives. This article will help troubleshoot three of the main issues unique to photographing while diving blackwater.

Phyllosoma and ctenophore. Larval animals often look nothing like their adult counterparts. This is a larval lobster carrying a ctenophore for reasons we cannot comprehend.

Focusing in Blackwater

Shooting gelatinous animals isn’t like photographing reef fish, corals or other typical subjects. As opposed to reef subjects that can hide against or behind objects in the substrata, pelagic animals have body structures that are designed to disappear in constantly moving open water.

One thing that will become pretty obvious from the moment you splash is that more light is better. Focus lights on a reef at night don’t have to be terribly bright to be effective, but gelatinous animals can soak up a lot of light before they appear in front of you. Also, try holding the light at an oblique angle to the camera. This will better illuminate odd angles on the animal better than lights that face directly forward.

Your camera’s sensor will be working extra hard to see through the backscatter to pick out the subtle contrasts and focus on the subject. It helps to have a DSLR with a dedicated focusing sensor, which in Canon and Nikon DSLRs is known as phase-detect AF. This passes a sample of light from the main aperture through a series of small lenses to produce two images. The distance between the images can be measured with a line sensor to tell the camera exactly where to focus. For comparison, contrast-detect AF is used in most compact and mirrorless cameras and is more of a trial and error process (Sony mirrorless cameras are the exception). Contrast-detect AF is much slower and can have a difficult time picking up clear plankton. Contrast-detect autofocus systems are at a disadvantage in the open ocean, but there are a few things you can do to help any camera system focus on what’s important.

One trick is to find the most contrasting point on the clear animal and place it on an autofocus point. This will force the camera to look at the animal instead of a piece of backscatter drifting between your port and the subject. And because the animal and photographer are affected differently by the movement of the ocean, keeping the autofocus mode on Al servo (or continuous focusing) will allow multiple shots of the same subject. 

Finally, some animals, such as the squid Megalocranchia, have highly contrasting pigment marks and body parts that the camera will want to pick up on instead of a preferred focusing point such as the eyes.  This brings us to the last tip to help focus on your subject. Many blackwater animals are very small and will be shot near the minimum focal distance for your macro lens. Because of this, it is helpful to use a wide depth of field with a very small aperture to help sharpen any mishaps in the focusing process and bring more of the subject into focus.  

Exocoetid. Many animals will reside within 10 inches of the water's surface. It can be very productive to spend some of your dive in just 5 or 10 feet of water looking up.

Strobes and Exposure

The two ways that small animals camouflage themselves in the open ocean is through clear gelatin and highly reflective body parts that blend in by bouncing available light back, matching the surrounding water almost perfectly. Some animals rely on both reflection and transparency. For a photographer striving to attain proper exposure, these two properties can prove be a nightmare. 

Open ocean animals almost invariably require an external strobe to illuminate properly. There are several benefits to using strobes. First, the wider beam angle illuminates clear animals better. Second, wide angled strobes reduce backscatter. Third, external strobes produce more light than onboard flashes, which in the case of gelatinous animals, means more detail in the final shot. Finally, external flashes enable the photographer to use direct, non-diffused light that will reflect off the gelatinous surfaces to better show the body forms.

One special case is when an animal such as a larval fish relies on both transparency and reflective body parts to blend in. In the case of the larval flounder, when the body is properly exposed, the eyes are blown out. Instead, it is preferable to expose for the eyes, thus preserving the detail in the raw image. The underexposed body details can then be brought back with the exposure bar in post-production.  Finally, use the burn tool (in Adobe Photoshop) to reclaim the details in the eye. 

Chascanopsetta prorigera. For animals that are both clear and reflective, expose for the reflective eye and bring back detail in the clear parts during post-processing.

Movement

The final challenge of the open ocean that must be overcome is the constant movement of everything in it. The boat moves differently from the divers that move differently from the plankton, and when that rare dolphin or shark does come through, they move much faster than anything else. It helps to understand what forces are acting on each element in order to be in the best position to capture the image.

A boat’s drift is a result of both current and windage. In the absence of wind, the boat and divers will move with the current at the same speed, giving the impression that there is no current at all. As soon as the wind picks up, however, the boat will act like a sail and drift in a different direction, dragging the divers with it. Animals will come flying out of the darkness in a unidirectional manner. To the divers, this will seem an awful lot like current. Many divers will just sit back and let the harnesses drag them around. The attentive divers, however, will swim against the apparent current until they come across an animal they wish to observe. Then they can simply drift back and photograph the animal until they reach the end of their down-line and are again being towed. This strategy gives photographers the most time with their subjects.

Controlling yourself in a soup of plankton is a somewhat different challenge. Small animals will be acted on by different forces than act on the divers, creating a somewhat chaotic effect that can be tough to follow through your eyepiece. Buoyancy and good body positioning are especially important when trying to focus on plankton. One errant fin kick or an unexpected stream of bubbles will not only ruin your shot, but probably destroy the animal you were trying to shoot. 

Finally, anything larger than a football (generally classified as nekton) is going to be able to move much faster than the clumsy divers. Blackwater divers are sometimes treated to the real rarities of the open blue such as tuna, dolphins, squids, and even oceanic sharks. There really is no big hint to getting into position for pelagic nekton except just being lucky. 

Xiphias gladius. Encounters with large nekton such as this swordfish are rare but can serve as a high point in just about any diving career.

Megalocranchia. You never know what you'll see when blackwater diving.

In Conclusion

Blackwater diving has a different draw for everyone. Some want to face the primal fear of the dark unknown. Others want to experience a whole community of animals they have never seen before. No matter how alien the pelagic environment may seem to us, billions of incredible life forms call it home. And that’s where the strange salp offers a sense of familiarity through a crucial body part called a notochord. In a watery world of sea freaks, it might be comforting to know that this harmless looking barrel-shaped organism is one of our most primitive relatives from a time when our distant ancestors had a spinal chord without any supportive skeleton. So when you look into the vast blackness and find a small pulsating ribbed drum, you will be forgiven if the first word that comes to mind isn’t “grandpa.”  But go ahead and give one a hug all the same.

Salp. Think of this salp as your distant cousin, only slimier.

Also by Jeff Milisen

• Ultimate Guide to Sea Turtle Photography

• Diving with Devils: the Ultimate Guide to Manta Rays

• Inside Look at Hawaii's Best Scuba Dives

• 5 Reasons to Dive Malapascua

Further Reading

• Manta Ray Night Dive in Kona, Hawaii

• Focus Lights for Underwater Photography

• Best Strobes for Underwater Photography