Octopus in Porthkerris

Posted on July 5, 2026 by An Bollenessor under bryozoans, crustaceans, diving, echinoderms, fisheye, molluscs, photography, Porthkerris, wide angle

This is the second year of an ‘octopus boom’ here in Cornwall. One of our two native species (Octopus vulgaris) has become much more common, probably due to warming waters. They wreak havoc on the crab pots (it is a big local story), but have made many snorkellers and divers very happy! Although I have spotted them once or twice before, this week I headed down to Porthkerris to have a proper look. Porthkerris is one of the best known shore dive sites in the country, and the only shoredive site in Cornwall I know of that let’s you get a bit deeper than ten meters. Those extra few meters make the difference in spotting things like Cuckoo Wrasse and Sea Fans, and also make it more likely to spot octopus (although these also occur in shallow water; one was even found in a rockpool in Falmouth). Armed with my 8mm fisheye lens I drove down on a Tuesday for two (solo)dives. It wasn’t long before I spotted the first octopus, however it quickly jetted away from me – either they have different personalities or different moods (or both) but not every octopus reacts the same to a passing diver. I managed to get a bunch of shots of several cooperative individuals shown below. Some individuals looked a bit ropey as they were nearing the end of their life-span and I even spotted a dead individual.

I managed shots of some other animals as well, see the gallery below (click on pics for legends). I have done much more macro- than wide-angle photography lately, as it is quite hard in murky English waters. When using strobes it is easy to get backscatter, moving very close to the subject minimises that but makes it hard to get any light between the dome and the subject, often resulting in an unlit centre of the shot and/or blown out spots at the sides. Anyway. I went back on Friday for another two dives. Fewer octopuses (octopi is incorrect!) and worse viz but enjoyable all the same. A selection of critters below. I found a nudibranch new to me (Acanthodoris pilosa) that was so large I could take a halfdecent photo of it using the fisheye lens!

Tompot Blenny

Posted on May 9, 2026 by An Bollenessor under diving, eggs, EMWL, fish, Silver Steps

Every time I dive at my local site Silver Steps, I check out a crack in the rocks that houses a variety of Crustaceans and fish (see for instance this old post). Yesterday I brought my fancy macro-wide angle probe lens specifically to look for a Tompot Blenny (Parablennius gattorugine). I found two, including this male guarding his eggs (visible at the back, top and bottom of the crack in the photo below). The last photo shows that these guys are pretty feisty too!

More Macro

Posted on April 24, 2026 by An Bollenessor under eggs, Macro, molluscs, nudibranchs

Has ‘an bollenessor’ turned into a macro photography-only blog? It seems so, I have not posted about my aquarium in ages. I still end up doing macrophotography when I go rockpooling. I tried wide-angle photography last week in the rockpools and failed miserably (so no photos for the blog). I hope to mix it up later in the year but for the moment here are some more macro photos. Above a picture I am quite pleased with: a solar-powered seaslug Elysia viridis on its favourite food the green seaweed Codium with some nice orange seaweed as a background. The pictures below show the snail Raphitoma purpurea (a first for me in Cornwall), the nudibranch Okenia nodosa (a lifer for me), a European Cowrie Trivia monacha and a patch of goby eggs (sans goby-egg eating seaslugs unfortunately).

I am a bit stuck in a limbo where on one hand I want to see interesting, new species and take good ID pictures (for recording on iNaturalist and sharing on facebook groups), but on the other hand I have gone a bit above my station and developed an interest in taking more ‘arty’ photos such as the solar-powered seaslug one at the top of this post. Sometimes the two aims converge. sometimes not. As an illustration of that, below a few shots of the nudibranch Polycera quadrilineata that ended up quite differently: a ‘good for ID’ photo but with an ugly cluttered background, a more arty photo (although the bokeh effect is due to backscatter and it is actually not that great), an overall ‘nice’ photo (posted before), a ‘shore studio’ shot of a slug (more about that in the next post) and an artsy fartsy version of a studio shot where the highlight have been so blown out that the slug basically is shown as a set of yellow stripes. I must say I can have ideas about how to take a certain shot, but my general approach is still ‘spray and pray’!

Early Spring Macro

Posted on March 29, 2026 by An Bollenessor under crustaceans, eggs, fish, Flushing, Macro, molluscs, mzuiko60mm, nudibranchs, rock pooling, seaweeds, shells, snorkeling, worms

High time for a quick update. Spring has not started in earnest yet and so the number of days in the water have been limited. As is usual, I have practiced taking pics of Flat Periwinkles (Littorina obtusata or L. fabialis) on a bank of the Penryn River. Below that another set of pics taken in Flushing and Falmouth when it was too windy and choppy to get in the water. These were all taken with my cygnustech diffuser which give the pictures a quite distinctive, slightly subdued look.

I did go in the water a few days in a row when the weather and tides allowed it, which was great. I think one time I stayed in for three hours – my core temperature took some time to recover! No special finds and only a few good pics as my strobe placement had become quite rusty but here are the best and/or the most interesting ones. (Species names in the photo captions.) Bring on proper spring weather and flat seas!

Black Backgrounds

Posted on February 25, 2026 by An Bollenessor under cnidarians, fish, jellies, molluscs, photography

Last year I gravitated to macrophotography – in part because of the mostly bad viz, and in part because of the lack of outings to deeper/more interesting dive sites. Although through necessity, this was not really a problem, as biodiversity is greater at the small scale and I find macrophotography a bit easier than wide angle photography (especially as I am not usually floating through crystalclear, sunlit waters with many ‘charismatic’ animals). One macro trick is to use black backgrounds, avoiding the clutter of gravel, seaweed and assorted debris around the subject. For this you need to light the topic with a strobe and have open water behind it (which cannot be lit up and hence remains black). (Another strategy is using a snoot but I never managed to get that working…) Most recent posts feature examples of this technique but here are three pics I did not get round to posting. Descriptions of animals can be found in the captions.

The black background method also works for wideangle photography. As a bonus I am reposting a collection of old jellyfish photos.

Crabby Camouflage

Posted on February 14, 2026 by An Bollenessor under crustaceans

I am frequently amazed by the ability of animals to be perfectly camouflaged. Here are three examples of local crab species that do an impressive job of blending in. Above, the Furrowed (or Pebble) Crab (Xantho hydrophilus). An abundant species – multiple individuals will hide under every rock you lift up on the shore. Below a Broad-clawed Porcelain Crab (Porcellana platycheles) which also lives under rocks, flat and covered in tiny hairs. (This is actually not a true crab but the product of ‘carcination’ where non-crabs have evolved into a crab-like form. This has happened independently in at least five Crustacean lineages.) Finally a Green Shore Crab (Carcinus maenas) which is abundant in many locations although not so much locally. There are even better examples of crab camouflage around, but I either do not have good photo of them (Spider Crabs decorating themselves with sponges and seaweeds), or have never seen them myself as they live in water deeper than I normally dive (the Sponge Crab).

What is a seaslug?

Posted on January 15, 2026 by An Bollenessor under Macro, molluscs, nudibranchs, worms

A nudibranch, a snail and a seaslug crawl into a bar…no seriously, what actually is the difference between these three types of molluscs? According to Kerney and Cameron (1979), those animals that cannot fit into their shell are called slugs, and those that can are called snails (definition brought under my attention by Ian Smith, see his amazing species accounts of British molluscs on flickr: Morddyn). Seaslugs either have an outer shell in which they cannot retract, an internal shell or no shell at all. The Solar-powered seaslug (Elysia viridis) pictured above is a species without a shell that is an example of a seaslug. Nudibranchs are a type of seaslug with ‘naked’ (nudi) gills (branchs) on their back. Nudibranchs never have a shell (although many have one when they are a larva). Books on nudibranchs often include seaslugs and sometimes they even feature snails! This happens when these species are related to seaslugs (the ‘lathe acteon’ or ‘beer barrel’ Acteon tornatilis is an example of that – a goal of this year is to take a good photo of that species). I have posted a range of photos on here as an illustrations of seaslugs (or not!); read the captions for species info.

Candy striped flatworm Prostheceraeus vittatus

Rainbow Seaslug

Posted on January 11, 2026 by An Bollenessor under molluscs, nudibranchs, snorkeling

Because it was only a few degrees I had opted for rockpooling instead of snorkeling, but as this was my chance, I left the overturned rock to walk back to the carch, ange into my wetsuit and run back. By gently lowering the rock in a pool I was able to take underwater photos. (Some people manage to submerge their camera only when they are out in waders but that approach just does not work for me.) Seaslugs are fairly slow but small (this one was maybe 15 mm) so it is not easy to photograph them. I always go through many aperture/ISO/shutterspeed/strobe output combinations before shots become acceptable. One way of shooting nudis is to use a very small aperture to get as much of the animal in focus, another is to use a larger aperture to only have (parts of) the head in focus, leaving behind the often cluttered background. I am still figuring out what works best for me!

Blue-rayed Limpets

Posted on January 8, 2026 by An Bollenessor under Uncategorized

Some snaps of Blue-rayed Limpets (Patella pellucida) from last year. I do not think I can improve much on an earlier photo of this species (see here) but I quite like the subtle colour patterns of the kelp on these photos. I have a whole bunch of images still to put on the blog however, I saw something very special the one time I went out this year and will probably post about that first! Btw, some photos see the light of day on instagram first, check: @an_bollenessor.