All images © Alex Mustard

We kit up on a small wooden bench at the back of the pickup truck, enclosed on all sides by the impenetrable green wall of the jungle. There is no view of water, our destination is just a wooden staircase leading down into crack in the earth. These are certainly surreal surroundings for scuba, but I am about to experience one of diving’s freshest experiences. The steps lead down into a pool of smooth, dark water, I slip in and dip my head into El Pit cenote. Suddenly I feel much smaller. This tiny plunge pool is the opening to a huge world, both underwater and underground. Looking down, I can see about 100ft, but I can’t see the bottom, in front this t-shaped cavern extends away into the darkness. Welcome to the world of photographic opportunities and challenges of cenote diving!

© Alex Mustard: Sunbeams in cenote, Garden of Eden Cenote – Nikon D5

Any BSoUPer looking to expand our photographic horizons, should place a trip to Mexico’s cenotes at the top of our list. The cenotes offer two types of diving: Cavern Diving is open to all and takes place always in view of the light from an entrance, although this still means going into some very dark spaces. Cave Diving is the technical discipline that requires special training and equipment, but allows divers to explore the fully dark and much less visited parts of the cenotes.

© Alex Mustard: Sunbeams in cenote, Chac Mool Cenote – Nikon D5

Full-blown cave diving gives a photographer access to the best cave formations, however the photographic potential of caverns should not be underestimated. All the images here are taken during cavern dives that any qualified diver can experience with a guide. Cavern areas still have reasonably attractive speleothems (stalactites, stalagmites etc) in the right places and have the big advantage that the beams of sunlight that penetrate at openings make the most attractive subject of all.

The cenotes are filled with very clear water, however, they are mostly very dark, which is the main photographic challenge and causes problems both for focusing and exposure. For focus, I use back-button or thumb-focus in the cenotes. This is a mode offered by most cameras that allows us to decouple the autofocus from the shutter release and assign it to a button you press with your right thumb. This means you can focus carefully when there is light at the start of the dive and then leave it locked, so that the focus does not struggle in darker places. Although we will, of course, be diving with a torch, a dedicated focus light is often a hindrance in this type of photography as its beam will show up in your pictures, because it is brighter than the dark conditions in the caverns.

© Alex Mustard: Sunbeams in cenote, Casa Cenote – Nikon D5

The main challenge of the darkness is with exposures because the required settings are way beyond what we normally use. For example, the photos here have ISOs well over 1000 and shutter speed slowed down to a very risky 1/13th to collect enough light!

© Alex Mustard: Sunbeams in cenote, Garden of Eden Cenote – Nikon D5

Sadly there are no magic numbers that I can tell you to plug in to work for all cenote shots. First, cenote light levels are very changeable. Second, how much each of us will adjust our aperture, shutter speed and ISO from our normal dive settings depends on our camera. For example, newer cameras can be pushed to higher ISO values than older ones. Full frame cameras can use higher ISOs, but also need the aperture closed more for acceptable corner sharpness. Image stabilized lenses and cameras can be pushed to slower shutter speeds, than non-stabilized lenses. And so on. What I can advise is that it is best to think about your settings and your camera’s capabilities pre-dive, rather than trying to make a call on what to sacrifice under pressure and underwater. Furthermore, it is sensible to compromise a little on all three (aperture, shutter speed and ISO) rather than a lot on any one control.

The key to capturing beautiful beams is to position ourselves in the dark, looking out to the beams. Crucial to success is to find a viewpoint that hides the surface and anything else brighter that the beams from the camera. This allows us to properly expose for the beams and to make them stand out. If we have to expose for the surface, the beams will be faint and hard to see. The other big challenge with exposure is getting it right! In the dark of a cavern, our LCD will shine brightly, making it easy for us to think an underexposed image is correct. Underexposing a little isn’t normally a problem when diving because we can easily tweak the exposure in Lightroom. However, in the cenotes we will be working with higher ISO values, which means image quality falls away much more quickly with any post processing corrections.

© Alex Mustard: Sunbeams in cenote, Dream Gate Cenote – Nikon D5

© Alex Mustard: Sunbeams in cenote, Dos Ojos Cenote – Nikon D5

I always dive in the cenotes with strobes attached to my housing, but I keep them turned off as much as possible. Adding strobe light usually ruins the feeling of atmosphere, so unless there is something spectacular in the foreground, don’t worry about lighting it up. The dark shapes of the caverns makes for an excellent frame when shooting towards light. Fisheye lenses are usually the default choice in caverns because the really open up the space. However, when shafts of light or stalactites run close to the edges of a fisheye shot they will bend. Careful composition keeps bendiness to a minimum, and we can always straighten them up in post processing using lens correction. However, when planning on shooting speleotherm formations I will often favour a non-bendy rectilinear lens to capture all that angular glory.

© Alex Mustard: Sunbeams in cenote, Dream Gate Cenote – Nikon D5

The best formations tend to be a little deeper inside cenotes where it is dark. If we only light them from the front they tend to look flat and blend with the background. This is where remote strobes come in. Off camera lighting is a powerful photographic technique, but also difficult with correct gear and massively frustrating when the equipment is imperfect. Practice with your remote strobe before you dive and triple check that the system is working! Using off-camera strobes is time and attention consuming, neither are good things in a dark, overhead environment. Remember that safe diving always comes ahead of photography and set modest goals.

Remote strobes can either be held by the model, pointing away from the camera to light up the background, or positioned behind the feature of interest on a plastic Gorillapod. The remote strobe creates much more depth in the total darkness of the cave, creating a more complete image. The perspective of the wide angle lens, makes the passageway look very tight for the diver, which helps make the image more dramatic and tell the story of this special diving location.

Alex’s Top Tips

1. All cenotes are on private land and require diving with a specially qualified guide. However, most guides are experienced and willing to pose for your photos and always have phenomenal buoyancy control and excellent trim.  Note that most cenotes ask photographers to pay a little extra for taking a camera in.

2. Cenote scenery is captivating, but nine times out of ten it looks best with a diver in the frame to give a sense of scale and a compositional focal point. Many serious photographers will dive with a private guide and ask them to model. Since dive gear is 99% black, people are easily lost in the background in a dark cavern. Position the model in front of the light coming in from an opening.

3. The complex shape of cenote openings and the trees surrounding them mean that the best beams come at very specific times of day in each cenote, and these shift a little during the year. All the good operators know when the beams are at their best in each cenote and will plan your diving accordingly, as long as you request it. You should also pay attention to the weather forecast on your phone, focusing on beams during periods of sun and shooting speleothems on cloudy days.