Underwater photography

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A United States Navy Mass Communication Specialist conducting underwater photography training US Navy 120209-N-XD935-302 Mass Communication Specialist 1st Class Shane Tuck, assigned to the Expeditionary Combat Camera Underwater Photo Team, c.jpg
A United States Navy Mass Communication Specialist conducting underwater photography training
Neon goby (Elacatinus oceanops) swimming over a great star coral (Montastraea cavernosa) Montastraea cavernosa (Great Star Coral) with Elacatinus oceanops (Neon Goby).jpg
Neon goby (Elacatinus oceanops) swimming over a great star coral (Montastraea cavernosa)
Wide-angle shot of coral reef in East Timor Reefscape.jpg
Wide-angle shot of coral reef in East Timor

Underwater photography is the process of taking photographs while under water. It is usually done while scuba diving, but can be done while diving on surface supply, snorkeling, swimming, from a submersible or remotely operated underwater vehicle, or from automated cameras lowered from the surface.

Contents

Underwater photography can also be categorised as an art form and a method for recording data. Successful underwater imaging is usually done with specialized equipment and techniques. However, it offers exciting and rare photographic opportunities. Animals such as fish and marine mammals are common subjects, but photographers also pursue shipwrecks, submerged cave systems, underwater "landscapes", invertebrates, seaweeds, geological features, and portraits of fellow divers.

Equipment

A Nikonos V amphibious camera Nikonos-V img 1851.jpg
A Nikonos V amphibious camera
Ikelite housing for SLR with dome port Ikelite Housing (Unsplash).jpg
Ikelite housing for SLR with dome port

Some cameras are made for use underwater, including modern waterproof digital cameras. The first amphibious camera was the Calypso, reintroduced as the Nikonos in 1963. The Nikonos range was designed specifically for use underwater. Nikon ended the Nikonos series in 2001 [1] and its use has declined, as has that of other 35mm film systems. Sea and Sea USA made the Motor Marine III, an amphibious range-finder camera for 35mm film. [2] [3]

Olympus TG-3 camera and its underwater housing front view Olympus TG-3 camera and its underwater housing front view P1240163.jpg
Olympus TG-3 camera and its underwater housing front view
A waterproof camera and waterproof light source setup for professional underwater photography Stahl Mermaids Production.jpg
A waterproof camera and waterproof light source setup for professional underwater photography
GoPro Hero5 action camera in underwater housing GoPro Hero5 Black.jpg
GoPro Hero5 action camera in underwater housing
Seaview SVII Camera using three dome ports for all round view Seaview SVII Camera.jpg
Seaview SVII Camera using three dome ports for all round view

Cameras made for dry work can also work underwater, protected by add-on housings, which are made for point and shoot cameras, compact cameras with full exposure controls, and single lens reflex cameras (SLRs). Most such housings are specific to the camera. Materials range from relatively inexpensive plastic to high-priced aluminum. Housings allow many options: users can choose housings specific to their everyday "land" cameras and use any lens. Underwater photographers generally use wide-angle lenses or macro lenses, both of which allow close focus and therefore a shorter distance to the subject, which reduces the loss of clarity to scattering. Digital media can hold many more shots than standard film (which rarely has more than 36 frames per roll). This gives digital cameras an advantage, since it is impractical to change film underwater. Other comparisons between digital and film photography also apply, and the use of film under water has declined, as it has on land.

Underwater housings have control knobs and buttons that reach the camera inside, allowing use of most of its normal functions. These housings may also have connectors to attach external flash units. Some basic housings allow the use of the flash on the camera, but the on-board flash may not be powerful enough or properly placed for underwater use. More-advanced housings either redirect the on-board strobe to fire a slave strobe via a fiber-optic cable, or physically prevent the use of the on-board strobe. Housings are made waterproof by silicone or other elastomer O-rings at the crucial joints and where control spindles and pushbuttons pass through the housing. High-end housings may use double O-rings on many of the critical pushbuttons and spindles to reduce the risk of leaks, which can destroy the electronics in cameras. Some cameras are inherently waterproof, or submersible to shallow depths; when these are in submersible housings, the consequences of a small leak are generally not serious.

There are optical problems with using cameras inside a watertight housing. Because of refraction, the image coming through the glass port will be distorted, especially with wide-angle lenses. A dome-shaped or fish-eye port corrects this distortion. Most manufacturers make these dome ports for their housings, often designing them to be used with specific lenses to maximize their effectiveness. The Nikonos series allowed the use of water-contact optics—lenses designed to be used submerged, without the ability to focus correctly when used in air. There is also a problem with some digital cameras, which do not have sufficiently wide lenses built in; to solve this, there are housings made with supplementary optics in addition to the dome port, making the apparent angle of view wider. Some housings work with wet-coupled lenses, which are screwed on to the outside of the lens port and increase the field of view; these lenses may be added or removed under water, allowing both macro and wide-angle photography on the same dive.

With macro lenses, the distortion caused by refraction is not a problem, so normally a simple flat glass port is used. Refraction increases the magnification of a macro lens; this is considered a benefit to photographers who are trying to capture very small subjects. Digital cameras may have several user selectable or programmable modes, which may include modes specifically for underwater use. [4]

Camera formats

Most types of digital camera have some underwater application. Those commonly seen in use are the models for which stock underwater housings are available, or which are inherently waterproof, such as rugged compact cameras, which may be used at shallow depths without a housing, but have housings available for greater depths. Compacts, rugged compacts and bridge cameras have great versatility regarding focal length, they tend to have a wide angle to telephoto lens with macro capabilities making these functions available without need to change lenses, which cannot be done during a dive. Although wet change accessories are available to increase or decrease focal length and for greater magnification, the 2020 generation rugged compacts already have inherent very close focus ability, and fairly wide angle low end of the focal length. Some of the rugged compact cameras will fit into a large dry suit or BC pocket in their underwater housing, though not usually with an external strobe or video light, allowing a diver to conveniently carry the camera on a working dive in case it may be useful, or for a larger format photographer to carry it as a backup.

Lighting

Graph of light absorption coefficient of pure water Water absorption coefficient large.gif
Graph of light absorption coefficient of pure water

Lighting for underwater photography has several aspects. There may be insufficient natural light to take a photo, in many cases the natural light has lost a significant part of the spectrum, or the photographer wishes to emphasize contrast between foreground and background. Where flash is used for the actual photograph, auxiliary light may be necessary or desirable to facilitate composition and focusing in low light conditions. Many digital cameras have video options, which require a steady light source, and in some cases a single video light can provide all these functions, and also serve as an adequate dive light for non-photographic applications.

The primary obstacle faced by underwater photographers is the loss of color and contrast when submerged to any significant depth. The longer wavelengths of sunlight (such as red or orange) are absorbed quickly by the surrounding water, so even to the naked eye everything appears blue-green. The loss of color increases not only vertically through the water column, but also horizontally, so subjects farther away from the camera also appear colorless and indistinct. This effect occurs in apparently clear water, such as that found around tropical coral reefs. [5]

Underwater photographers solve this problem by combining two techniques. The first is to get the camera as close to the photographic subject as possible, minimizing the horizontal loss of color. Many serious underwater photographers consider any more than about one yard or meter unacceptable. The second technique is the use of a flash to restore colour lost to depth. Fill flash, used effectively, "paints" in missing colors by providing full-spectrum visible light to the overall exposure. [6]

Another environmental effect is range of visibility. The water is seldom optimally clear, and the dissolved and suspended matter can reduce visibility by both absorption and scattering of light.

Underwater flash

Wide-angle image of French angelfish with proper balance between flash and sunlight Uwangelfish.jpg
Wide-angle image of French angelfish with proper balance between flash and sunlight

The use of a flash or strobe is often regarded as the most difficult aspect of underwater photography. Some misconceptions exist about the proper use of flash underwater, especially as it relates to wide-angle photography. Generally, the flash should be used to supplement the overall exposure and to restore lost color, not as the primary light source. In situations such as the interior of caves or shipwrecks, wide-angle images can be 100% strobe light, but such situations are fairly rare. Usually, the photographer tries to create an aesthetic balance between the available sunlight and the strobe. Deep, dark or low visibility environments can make this balance more difficult, but the concept remains the same. Many modern cameras have simplified this process through various automatic exposure modes and the use of through-the-lens (TTL) metering. The increasing use of digital cameras has reduced the learning curve of underwater flash significantly, since the user can instantly review photos and make adjustments.

Color is absorbed as it travels through water, so that the deeper you are, the less reds, oranges and yellow colors remain. The strobe replaces that color. It also helps to provide shadow and texture, and is a valuable tool for creativity.

Underwater photograph using internal flash illustrating backscatter Backscatter example P1066667.JPG
Underwater photograph using internal flash illustrating backscatter

An added complication is the phenomenon of backscatter, where the flash reflects off particles or plankton in the water. Even seemingly clear water contains enormous amounts of this particulate, even if it is not readily seen by the naked eye. The best technique for avoiding backscatter is positioning the strobe away from the axis of the camera lens. Ideally, this means the flash will not light up the water directly in front of the lens, but will still strike the subject. Various systems of jointed arms and attachments are used to make off-camera strobes easier to manipulate.

Strobes positioned to reduce backscatter Sponge diver.jpg
Strobes positioned to reduce backscatter

When using macro lenses, photographers are much more likely to use 100% strobe light for the exposure. The subject is normally very close to the lens, and the available sunlight is usually not sufficient.

There have been some attempts to avoid the use of artificial light entirely, but these have mostly failed. In shallow water, the use of custom white-balance provides excellent color without the use of strobe. In theory one could use color filters to overcome the blue-green shift, but this can be problematic. The amount of shift would vary with depth and turbidity, and there would still be a significant loss of contrast. Many digital cameras have settings that will provide color balance, but this can cause other problems. For example, an image shifted toward the "warm" part of the spectrum can create background water which appears gray, purple or pink, and looks unnatural. There have been some successful experiments using filters combined with the raw image format function on some high-end digital cameras, allowing more detailed manipulation in the digital darkroom. This approach will probably always be restricted to shallower depths, where the loss of color is less extreme. In spite of that, it can be effective for large subjects such as shipwrecks which could not be lit effectively with strobes.

Macro image of a Whitemouth Moray Eel using 100% flash for the exposure Gymnothorax meleagris head.jpg
Macro image of a Whitemouth Moray Eel using 100% flash for the exposure

Natural light photography underwater [7] can be beautiful when done properly with subjects such as upward silhouettes, light beams, and large subjects such as whales and dolphins.

Although digital cameras have revolutionized many aspects of underwater imaging, it is unlikely that flash will ever be eliminated completely. From an aesthetic standpoint, the flash emphasizes the subject and helps separate it from the blue background, especially in deeper water. Ultimately the loss of color and contrast is a pervasive optical problem that cannot always be adjusted in software such as Photoshop.[ citation needed ]

Snoot

A snoot is a tube used to direct the illumination from the flash to a very restricted area, strongly illuminating the area of focus and leaving the surroundings relatively dark. It is used to selectively illuminate the subject to give dark backgrounds and a brightly lit subject. It is easier to use if the flash has an integral modeling light so the photographer can see how the illumination will be distributed during exposure. A snoot with the opening placed close to the subject at an angle can virtually eliminate backscatter.

Modeling lights

A modeling light is a low intensity light used to compose the picture when flash is intended for illumination. I allows a better view of the subject for focusing and framing the shot. but does not provide enough light to interfere with the flash illumination. Some flash units have integral modeling lights, otherwise a diffuse low power dive light may work well for close up work.

Video lights

A video light is a powerful light source used primarily for shooting video in environments with insufficient natural light, but can also be used as the primary light source for still photography. Placement of the video light follows the same recommendations as for flash photography, with the advantage that the illumination can be clearly seen and assessed before exposure. Considerably more energy is required for constant illumination in comparison with flash, and this method is best suited to cameras with sufficiently sensitive CCDs and for close up work. Another advantage is that the video light provides good illumination for general diving purposes. Video lights with adjustable intensity can be even more versatile. Video lights tend to be mounted similarly to flash. The intense light may disturb light sensitive animals, and they may react by retreating from the source.

Split images

Another format considered part of underwater photography is the over/under or split image, a composition that includes roughly half above the surface and half underwater, with both in focus. One of the pioneers of the traditional technique was National Geographic photographer David Doubilet, who used it to capture scenes above and below the surface simultaneously. Split images are popular in recreational scuba magazines, often showing divers swimming beneath a boat, or shallow coral reefs with the shoreline seen in the background.

Over/under shots present some technical challenges beyond the scope of most underwater camera systems. Normally an ultra wide angle lens is used, similar to the way it would be used in everyday underwater photography. However, the exposure value in the above water part of the image is often higher (brighter) than in the one underwater. There is also the problem of refraction in the underwater segment, and how it affects the overall focus in relation to the air segment. There are specialized split filters designed to compensate for both of these problems, as well as techniques for creating even exposure across the entire image.

However, pro photographers often use extremely wide or fisheye lens that provides extensive depth of field - and a very small aperture for even more extensive depth of field; this is intended for acceptably sharp focus both on the nearby underwater subject and the more distant elements above water. An external flash can also be very useful underwater, on a low setting, to balance the light: to overcome the difference in brightness of the elements above and below the water.

Over/under photos necessitate the lens or port to be partly below and partly above the surface. When bringing the outer optical surface out of the water, droplets can be left on the surface which can distort the image. This can be avoided to some extent by wiping off the droplets with a chamois leather cloth above the water and lowering the camera to working position. Keeping the port fully wet is an alternative option, which requires the shot to be taken before the water on the top part of the lens surface separates into droplets. Which approach works better will depend on the surface tension of water on the lens surface.

David Doubilet explained his technique for split field images in an interview for Nikon Corporation. "You need to use a D-SLR and a super wide-angle or fisheye lens and a sophisticated housing that has a dome, not a flat port. Underwater images are magnified by 25 percent, and the dome will correct for that. The technique requires a small f/stop—f/16 or smaller—for great depth of field, plus a lens capable of close-focus; you always focus on the subject below the water line. You also have to balance the light. I look for a light bottom—white sand is best—or a light underwater subject. I'll put the strobes down below and light the bottom and then expose for the top. If you shoot at, say, ISO 400, you'll have plenty of exposure for the top, and the strobes will take care of the bottom. Of course, you need subjects that suit the technique." [8]

Digital darkroom techniques can also be used to "merge" two images together, creating the appearance of an over/under shot.

Applications

Skills and training

Since underwater photography is often performed while scuba diving, it is important that the diver-photographer be sufficiently skilled so that it remains a reasonably safe activity. Good scuba technique also improves the quality of images, since marine life is less likely to be scared away by a calm diver, and the environment is less likely to be damaged or disturbed by a diver competent in buoyancy, trim, and maneuvering skills. There is the possibility of encountering poor conditions, such as heavy currents, tidal flow, or poor visibility. Underwater photographers usually try to avoid these situations if reasonably practicable, but in many cases the desired subject can only be accessed under less than ideal conditions and the photographer must deal with reality. Underwater diving training providers provide courses to help improve divers' diving skills and underwater photography skills. [9] Good diving skills are necessary to avoid damaging the environment when maneuvering close to benthic subjects on reefs. Some underwater photographers have been implicated in reef damage. [10]

Scientific potential

Underwater photography has become more and more popular since the early 2000s, resulting on millions of pictures posted every year on various websites and social media. This mass of documentation is endowed with an enormous scientific potential, as millions of tourists possess a much superior coverage power than professional scientists, who can not allow themselves to spend so much time in the field. As a consequence, several participative sciences programs have been developed, supported by geo-localization and identification web sites (such as iNaturalist), along with protocols for auto-organization and self-teaching aimed at biodiversity-interested snorkelers, in order for them to turn their observations into sound scientific data, available for research. This kind of approach has been successfully used in Réunion island, allowing for tens of new records and even new species. [11]

Timeline

Paul Bartsch with underwater camera (1926) Paul Bartsch with undersea camera 1926.jpg
Paul Bartsch with underwater camera (1926)
Jacques-Yves Cousteau, pioneer of scuba diving and underwater photography and film-making. Bos en Kalis geeft personferentie in Den Haag over eilandenproject voor industri, Bestanddeelnr 925-4954.jpg
Jacques-Yves Cousteau, pioneer of scuba diving and underwater photography and film-making.
Norwegian diving pioneer Odd Henrik Johnsen with underwater camera (1960s) Odd Henrik Johnsen Scuba Diving.jpg
Norwegian diving pioneer Odd Henrik Johnsen with underwater camera (1960s)
Agnes Milowka. Agnes Milowka by J Axford.jpg
Agnes Milowka.

Notable underwater photographers

See also

Related Research Articles

Single-lens reflex camera Camera that typically uses a mirror and prism system

A single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system that permits the photographer to view through the lens and see exactly what will be captured. With twin lens reflex and rangefinder cameras, the viewed image could be significantly different from the final image. When the shutter button is pressed on most SLRs, the mirror flips out of the light path, allowing light to pass through to the light receptor and the image to be captured.

Camera Optical device for recording images

A camera is an optical instrument that captures a visual image. At their most basic, cameras are sealed boxes with a small hole that allows light in to capture an image on a light-sensitive surface. Cameras have various mechanisms to control how the light falls onto the light-sensitive surface. Lenses focus the light entering the camera, the size of the aperture can be widened or narrowed to let more or less light into the camera, and a shutter mechanism determines the amount of time the photosensitive surface is exposed to the light.

Shutter speed The length of time when the film or digital sensor inside a camera is exposed to light

In photography, shutter speed or exposure time is the length of time that the film or digital sensor inside the camera is exposed to light when taking a photograph. The amount of light that reaches the film or image sensor is proportional to the exposure time. 1500 of a second will let half as much light in as 1250.

Exposure (photography) Amount of light captured by a camera

In photography, exposure is the amount of light per unit area reaching a frame of photographic film or the surface of an electronic image sensor, as determined by shutter speed, lens aperture, and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region.

Flash (photography) Device producing a burst of artificial light

A flash is a device used in photography producing a flash of artificial light at a color temperature of about 5500 K to help illuminate a scene. A major purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the electronic flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. Modern cameras often activate flash units automatically.

Underwater videography The branch of electronic underwater photography concerned with capturing moving images

Underwater videography is the branch of electronic underwater photography concerned with capturing underwater moving images as a recreational diving, scientific, commercial, documentary, or filmmaking activity.

In photography, bracketing is the general technique of taking several shots of the same subject using different camera settings. Bracketing is useful and often recommended in situations that make it difficult to obtain a satisfactory image with a single shot, especially when a small variation in exposure parameters has a comparatively large effect on the resulting image. Given the time it takes to accomplish multiple shots, it is typically, but not always, used for static subjects. Autobracketing is a feature of many modern cameras. When set, it will automatically take several bracketed shots, rather than the photographer altering the settings by hand between each shot.

Backscatter (photography)

In photography, backscatter is an optical phenomenon resulting in typically circular artifacts on an image, due to the camera's flash being reflected from unfocused motes of dust, water droplets, or other particles in the air or water. It is especially common with modern compact and ultra-compact digital cameras.

Guide number

When setting photoflash exposures, the guide number (GN) of photoflash devices is a measure photographers can use to calculate either the required f‑stop for any given flash-to-subject distance, or the required distance for any given f‑stop. To solve for either of these two variables, one merely divides a device's guide number by the other.

In photography, through-the-lens (TTL) metering refers to a feature of cameras whereby the intensity of light reflected from the scene is measured through the lens; as opposed to using a separate metering window or external hand-held light meter. In some cameras various TTL metering modes can be selected. This information can then be used to set the optimal film or image sensor exposure, it can also be used to control the amount of light emitted by a flash unit connected to the camera.

Wildlife photography

Wildlife photography is a genre of photography concerned with documenting various forms of wildlife in their natural habitat.

Nikonos Brand of 35mm film amphibious cameras

Nikonos is the brand name of a series of 35mm format cameras specifically designed for underwater photography launched by Nikon in 1963. The early Nikonos cameras were improvements of the Calypso camera, which was an original design by Jacques-Yves Cousteau and Belgian engineer Jean de Wouters. It was produced in France by La Spirotechnique until the design was acquired by Nikon to become the Nikonos. The Nikonos system was immensely popular with both amateur and professional underwater photographers. Its compact design, ease of use, and excellent optical quality set the standard for several decades of underwater imaging. Nikon ceased development and manufacture of new Nikonos cameras in 2001, but the camera remains popular, and there is a large and active secondary market.

David Doubilet is an underwater photographer known primarily for his work published in National Geographic Magazine where he is a contributing photographer and has been an author for 70 feature articles since 1971. He was born in New York City and started taking photos underwater at the young age of 12. He started with a Brownie Hawkeye in a rubber anesthesiologist's bag to keep the water out of the camera. He lived with his family in New York City and spent summers in Elberon New Jersey exploring the Atlantic. He later worked as a diver and photographer for the Sandy Hook Marine Laboratories in New Jersey and spent much of his youth in the Caribbean as a teenage dive instructor in the Bahamas where he found his motivation to capture the beauty of the sea and everything in it. His wife is the photographer, Jennifer Hayes.

Portrait photography Type of photography aimed at expressing the personality of the human subject(s)

Portrait photography, or portraiture, is a type of photography aimed toward capturing the personality of a person or group of people by using effective lighting, backdrops, and poses. A portrait photograph may be artistic or clinical. Frequently, portraits are commissioned for special occasions, such as weddings, school events, or commercial purposes. Portraits can serve many purposes, ranging from usage on a personal web site to display in the lobby of a business.

Night photography

Night photography refers to the activity of capturing images outdoors at night, between dusk and dawn. Night photographers generally have a choice between using artificial lighting and using a long exposure, exposing the shot for seconds, minutes, or even hours in order to give photosensitive film or an image sensor enough time to capture a desirable image. With the progress of high-speed films, higher-sensitivity digital sensors, wide-aperture lenses, and the ever-greater power of urban lights, night photography is increasingly possible using available light.

The following outline is provided as an overview of and topical guide to photography:

Underwater vision Effects of the underwater environment on (human) vision

Underwater, objects are less visible because of lower levels of natural illumination caused by rapid attenuation of light with distance passed through the water. They are also blurred by scattering of light between the object and the viewer, also resulting in lower contrast. These effects vary with wavelength of the light, and color and turbidity of the water. The vertebrate eye is usually either optimised for underwater vision or air vision, as is the case in the human eye. The visual acuity of the air-optimised eye is severely adversely affected by the difference in refractive index between air and water when immersed in direct contact. Provision of an airspace between the cornea and the water can compensate, but has the side effect of scale and distance distortion. The diver learns to compensate for these distortions. Artificial illumination is effective to improve illumination at short range.

Architectural photography is the sub genre of the photography discipline where the primary emphasis is made to capturing photographs of buildings and similar architectural structures that are both aesthetically pleasing and accurate in terms of representations of their subjects. Architectural photographers are usually skilled in the use of specialized techniques and cameras for producing such specialized photography.

Dive light Light used underwater by a diver

A dive light is a light source carried by an underwater diver to illuminate the underwater environment. Scuba divers generally carry self-contained lights, but surface supplied divers may carry lights powered by cable supply.

Underwater photography is a scuba-based underwater sport governed by Confédération Mondiale des Activités Subaquatiques (CMAS) where teams of competitors using digital underwater camera systems all dive at the same saltwater ocean sites at the same time over a two-day period. The submitted digital images are then assessed and ranked by a jury using a maximum of five photographic categories as well as an overall score. The sport was developed prior to 1985 as a photographic film-based event and is currently mainly practised in non-English speaking countries.

References

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  2. "Sea and Sea". Sea and Sea. Retrieved 2012-06-20.
  3. Staff. "Motor Marine III Instruction Manual" (PDF). Sea and Sea. Retrieved 7 November 2016.
  4. "Olympus TG-6 Underwater Camera Review" . Retrieved 16 December 2020.
  5. Deep-six.com Color underwater
  6. Scott Gietler Underwater Photography Guide Lighting with Strobes
  7. "Natural Light Photography" . Retrieved December 25, 2013.
  8. "Underwater Photography Tips for Getting Started". Nikon. Nikon Inc. 2016. Retrieved December 11, 2016.
  9. PADI Course Flowchart
  10. Sink, K. (October 2004). Appendix 2. Threats affecting marine biodiversity in South Africa (PDF). South African National Spatial Biodiversity Assessment 2004: Technical Report Vol. 4 Marine Component DRAFT (Report). pp. 97–109.
  11. Bourjon, Philippe; Ducarme, Frédéric; Quod, Jean-Pascal; Sweet, Michael (2018). "Involving recreational snorkelers in inventory improvement or creation: a case study in the Indian Ocean". Cahiers de Biologie Marine. 59: 451–460. doi:10.21411/CBM.A.B05FC714.
  12. Cárdenas, Fabricio (2014). 66 petites histoires du Pays Catalan[66 Little Stories of Catalan Country] (in French). Perpignan: Ultima Necat. ISBN   978-2-36771-006-8. OCLC   893847466.
  13. "Thirty leagues under the sea". The Independent. Nov 2, 1914. Retrieved July 24, 2012.

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