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Dive Photo Guide


Blackwater Blankets
By Alex Tyrrell, July 24, 2023 @ 06:00 AM (EST)

Blanket statement: An adult female blanket octopus demonstrating how the species got its common name, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

Octopuses have always been a highly ranked subject for underwater photographers, but there are levels to their appeal, with certain species gaining more attention than others. If there was an Octopus Hall of Fame, previous chart-toppers would surely include the venomous beauty, the blue-ringed octopus; the shape-shifting mimic octopus; and the more recently described wunderpus, which has the best scientific name of all cephalopods—Wunderpus photogenicus.

In the last few years, a new contender to this crown has emerged, punching her way to the top spot. Meet the blanket octopus—Tremoctopus sp.—whose attraction is twofold: They are rare and very elusive. Every photographer wants a photo of a subject that is not commonly encountered so they can show off to their friends! Ultimately though, it’s the sheer beauty of this remarkable cephalopod that has propelled a meteoric rise up the rankings. When a blanket octopus unfurls her ludicrously colorful blanket, it is a sight to behold. There is nothing that compares to the gaudiness of this supermodel’s outfit; we have a new GOAT—Greatest Octopus of All Time!

The diminutive and much less flashy male blanket octopus, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, f/32, 1/250s, ISO400)

The explosion of blackwater diving over the last decade has seen the number of encounters of this species increase from “once in a blue moon” to “infrequently.” To put this into perspective, in the hundreds of blackwater dives I have completed, I have encountered the smaller male blanket octopus on perhaps six dives, the more-coveted females on only four dives—three of these being sightings from a single red-hot week in Anilao in April 2023. These are not an everyday encounter!

Blanket Facts*

Blanket octopuses are a pelagic species, living their entire life cycle in open water. This makes them hard to find and even harder for scientists to study in their natural environment. There are four species in the genus:  

  • Tremoctopus gelatus: a gelatinous deep water species from tropical and temperate waters
  • Tremoctopus robsoni: known from the waters off of New Zealand
  • Tremoctopus gracilis: palmate octopus found in the Indo-Pacific region
  • Tremoctopus violaceus: violet octopus found in the Atlantic

Their life cycle can last up to five years, exceptionally long for a cephalopod, and they have been observed hunting in the same area for an extended period of time. Being a pelagic animal means they don’t make a burrow in the sand or create a home like other octopuses do. These octopuses mate, hunt, feed and thrive in the open ocean and can roam from the depths of the dark zone to the surface, truly masters of their open ocean domain.

Unique in appearance and unique in behaviour, the Tremoctopus is immune to the deadly nematocysts of many cnidarians, including the man o’war jellyfish. It is reported that juvenile Tremoctopus rip the stinging tentacles from the jellyfish and then hold them with their lateral arms, whipping them about to sting their prey and perhaps to protect themselves. Many photos show the trailing tentacles and clearly illustrate that this is indeed a common behavior.

*These facts are an abbreviated excerpt from Mike Bartick’s excellent book, The World of Blackwater, which is essential reading for any blackwater enthusiast. It is available on Apple Books and Gumroad.

A partially unfurled female blanket octopus, Lembeh Strait, Indonesia (Nikon D500, Nikon 60mm f/2.8 macro, f/32, 1/250s, ISO400)

The sexual behavior is also fascinating. The male of the species exhibits a higher degree of dimorphism than any animal yet to be discovered. The female can measure up to six-and-a-half feet in length, while the males only reach a size 20mm—less than an inch—a size/weight ratio of as much as 10,000 times! Male Tremoctopus uses a specialized arm called the hectocotylus, like other male octopuses, which contains its sperm pack. The male only then needs to touch the female with this specialized arm, as it instantly sticks to her and then snaps off—perhaps without her even knowing.

The arm then creeps down or somehow finds its way into the ovum of the female where she crushes it, releasing the sperm and fertilizing her eggs when the time is right. Hatching is intermittent. The male, like other octopuses, having completed his life’s work, now dies. However, the female still has a long life ahead, brooding and caring for her eggs, until she finally dies from starvation much like other, more familiar octopus species.

Tremoctopus gets its common name from the blanket that it can quickly unfurl and retract. The texture of the blanket looks like an exaggerated version of the webbing that a common octopus has and uses to web over their prey when hunting. However, these guys deploy the blanket to make themselves look bigger and perhaps to hunt and catch crustaceans or other cephalopods like the paper nautilus. The thin membrane is colorful and ocellated, much like the feathers of a peacock, with a pink, purple-green hue. They can also detach their webbing to ensnare a would-be predator or to evade as well as ink.

A large female blanket octopus cruising through the night, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)


Where to See

As already mentioned, you can encounter blanket octopuses in a variety of locations, though not all areas have dive operations offering blackwater diving. By far the most common destination for them to be seen is Anilao in the Philippines. This may be partly due to more operators offering blackwater dives in this area, which in turn puts more eyes out there to find them.

Other Indo-Pacific locations I know they have been seen are Romblon in the Philippines, and both Lembeh and Ambon in Indonesia. On rarer occasions, blankets will be seen on blackwater dives in the Gulf Stream, out of West Palm Beach, Florida. I have also read of them being seen off the Great Barrier Reef on the east coast of Australia, the Gulf of Mexico, and the Mediterranean Sea. 

Blanket Behavior

When you are on a dive and a blanket octopus turns up, be prepared for potential chaos. They are very quick when they want to be, so it’s time to shift up a couple of gears to stay with them. Unlike humans, blanket octopuses do not have any of the constraints of equalizing or decompression sickness, so can rapidly dive into the depths, leaving you with painful ears, or more dangerously, cause a diver to ascend at speeds way faster than are safe.

Care must be taken and special attention paid to no-decompression limits, air consumption, and maximum operating depths if they head downwards. If they shoot for the surface, divers must be extra careful with ascent rates. If the latter, it is much safer to stop shooting, use your dive light to keep track of them while ascending at a normal speed, and then recommence shooting when you have caught back up.

A female blanket octopus with the blanket retracted, Lembeh Strait, Indonesia (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

If you hit the jackpot and get a relaxed supermodel that happily poses for multiple shots, make the most of it—you’ve found gold! Use this opportunity to shoot at different angles and capture different poses, but be ever ready to capture the money shot if the blanket is revealed. If you are not alone, take turns shooting rather than it turning into a “free for all.” You will all get better shots this way. Be aware to not ruin others’ shots when you’re not shooting: Don’t swim underneath them, creating a cloud of bubbles; stay out of their backgrounds; and don’t shine your light onto the subjects or into their lens.

Camera Equipment and Settings

Given that an encounter with a blanket octopus is anything but guaranteed, setting up in a dedicated wide-angle configuration, specifically to shoot a subject their size, would mean missing out on many other blackwater photo opportunities, given that most other subjects require a macro setup.

The go-to lens for blackwater is a 50mm/60mm macro lens that focuses close and fast, giving a 1:1 (or near to) reproduction ratio. Longer lenses in the 100mm/105mm range are usable but will make your life harder. Up until recently, due to autofocus performance and suitable lenses, the most popular blackwater setup was a Nikon D850 or Nikon D500 combined with the Nikon 60mm macro lens, though with the recent release of the Nikon Z8, Sony a7R Mark V, and the forthcoming Canon EOS R5 Mark II, your options are certainly not limited to Nikon DSLRs anymore.

A small female blanket octopus, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

If you are shooting a full-frame camera, you will find that the 60mm lens will adequately accommodate the proportions of all but the largest individuals. But I found that shooting Nikon DX (ASP-C) format, with the 1.5 crop factor, you need to back off a little too far to fit the subject in the frame. And more distance equals more backscatter.

This is where the Kraken KRL-09S wide-angle conversion lens comes into play. (The Nauticam MWL-1 does the same job, just at more than double the price.) I have this mounted onto my D500 (for blackwater, I prefer the D500’s DX sensor and speedy AF over the D850) on a flip adapter, so if the occasion arises to shoot something bigger, it is a simply a matter of flipping the lens down into position and then quickly adjusting strobe position for the wider frame. This lens gives you 154° field of view when combined with a 60mm on an FX (full-frame) sensor, so is less on DX, but it is perfect for a subject the size of a blanket octopus. You can get much closer, cutting down the water column between the lens and subject for greatly reduced backscatter and sharper, more colorful images.  

Lighting can be achieved from any good-quality strobe, with soft, even lighting being optimal, so use diffusers to help reduce reflected highlights. A fast recycle time is beneficial for speedy shooting, allowing you to capture more correctly exposed frames in brief moments of action. You don’t want to be missing the shot as the blanket unfurls due to your flash not recycling quickly enough! I use Retra Pro X with the added Supercharger battery packs to halve my recycle times, plus the soft diffusers. An LED flash trigger, or electronic sync cords, are a better option than shooting with the camera’s pop-up flash, as the on-board flash has a slower recycle time, which will then become the deciding factor on shooting speed. You can normally decrease the power of the on-board flash to speed things up if this is your only option.

A partially unfurled female blanket octopus, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

Blanket on full display, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

The best autofocus mode will depend on your specific camera. For blackwater shooting with my D500, I exclusively use the Continuous-Servo 3D Tracking mode. I have found this best for tracking the smaller critters, while at the same time not being detrimental for larger subjects where another AF mode could perform better. I don’t want to be wasting time adjusting unnecessary camera settings when a blanket turns up; I need to react quickly, getting into a shooting position while simultaneously moving the strobes wider and flipping the wet lens into position.


The stand-out feature of a female blanket octopus is understandably the colorful membrane possessed between its arms; they can easily be mistaken for a more common species if the blanket is not visible. Don’t refrain from shooting when the blanket is retracted though, as they are still photogenic, but a shot with the “blanket” on display is the ultimate goal.

If the blanket is missing, it is the equivalent of your catwalk supermodel whipping off her Versace dress and revealing a Primark tracksuit underneath—she’s still pretty but looked a lot better in the designer outfit! However, even if you are lucky enough to encounter this stunning cephalopod, there is no guarantee that she will unfurl the blanket. If she does, it will quite probably be for a brief moment, so in addition to being lucky, you’ll need to be on the ball if it happens, to ensure you are in the right position to capture the shot.

The cool, but much less “sexy” of the blanket octopus genders, the male, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, f/25, 1/250s, ISO400)

A side-on shooting angle is what I am aiming for the majority of the time, as this shows the shape of the octopus, gives strong eye contact and, if the blanket is unfurled, this will become the center of interest. Partially angled shots also work well, as this can still show the colorful blanket while maintaining good eye contact. A head-on shot isn’t as effective for me, though can still show shape and color, but doesn’t normally have strong eye contact, leading to a weaker composition. If you are extra lucky, whereby you encounter one at or near the surface, you should strive to incorporate surface ripples and texture into the composition, creating a more interesting background than plain black. If you have calm enough surface conditions, look to capture reflections by shooting at a slightly upward angle (but not too steep) to the surface.

A female blanket octopus poses in front of a diver, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

In April this year, whilst staying at Crystal Blue Resort in Anilao with Mike Bartick, we were treated to a hot week, giving us encounters with blanket octopuses on three separate dives. The final encounter was brief and chaotic, giving us a minute of mayhem when four blanket octopuses showed up at the same time! Our guide, Jhomel, spotted them swimming down from the surface and frantically signaled Mike and me over.

Mike was a fraction ahead of me and went to one on the left, so I went right. But they had our number, and with both of our eyes glued to the viewfinder taking away our peripheral vision, they comically guided us both into each other, then sped away. I only managed two frames before they were gone, leaving me blowing big clouds of bubbles after a 100-meter sprint at 32 meters! Upon checking my shots after the dive, I had just about managed to capture a frame with a second blanket visible in the background. Granted, it’s not the best shot, but it’s a great memento of a very cool, albeit brief, encounter. It was the first time Mike had seen adult females together.

A duo of female blanket octopuses keeping their namesake “blankets” hidden, Anilao, Philippines (Nikon D500, Nikon 60mm f/2.8 macro, Kraken KRL-09S, f/32, 1/250s, ISO400)

The dive season in Anilao runs from November through to June, though peak season is from January to April. Blanket octopuses are encountered at any time of year, though this past April was particularly good, with multiple sightings over subsequent days. If you would like to join Mike and Alex next year at Crystal Blue Resort in Anilao, they have a special “Blackwater Week” planned for April 2nd–9th, where they will complete critter dives during the daytime and then two blackwater dives every night. If you would like further information or are interested in joining, please contact Alex at alex@dive4photos.com for more information.

Alex Tyrrell is a professional underwater photographer and underwater photography instructor based on Koh Tao, Thailand. His company Dive4Photos teaches all levels of image-makers how to improve their diving and photo skills. To see more of Alex’s vast portfolio of images, check out his website, www.atyrrell.com.



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