DESCENDING TO 25m on a kelp-covered rocky slope, we made our way north before stumbling onto a spectacular wall plastered in an extravagant profusion of life.
Covered from top to bottom in delicate, multi-coloured anemones, soft, vibrant sponges, radiant golden tunicates and luxuriant swathes of dead-men’s fingers, wispy hydroids
and matts of bryozoans, macro life was in such abundance that not a centimetre of bare rock could be seen.
Forty-one miles north of the Butt of Lewis in the Outer Hebrides, two rocks rise out of the north Atlantic. One is North Rona; the other, 11 miles away to the north-east, is Sula Sgeir. Together they are arguably the most remote islands in the British Isles.
Battered by massive Atlantic storms, Lewismen used to row the 41 miles in an open six-oared boat, without compass, to collect juvenile gannets for the meat known as guga.
These men are known as the guga-hunters, and even today they make the annual trip to these islands in search of this delicacy.
Twelve divers met the mv Halton on a calm Saturday evening in Scrabster, on the north coast of mainland Scotland. A 21m converted trawler, the Halton is a rugged vessel built to withstand the worst of weather. It has a modern navigation system, spacious galley (including an oil Rayburn cooker) and six comfortable twin-berth cabins.
Skipper Bob Anderson is a seasoned and experienced operator and diver around the northern isles.
Supported by Seasearch, one of the aims of our expedition was to record the marine flora and fauna around North Rona and Sula Sgeir.

CAPE WRATH
Before heading to the islands, we took the opportunity to warm up at a couple of sites just off the north-west Scottish mainland, a short two-hour steam from Scrabster, and not far from Cape Wrath.
The area is known for its rich marine life, clear Atlantic water and dramatic scenery. We saw dolphins and basking sharks along the way, and went in to explore a series of big gullies lined with large, healthy kelp and a colourful profusion of life.
Multi-coloured jewel anemones, bright yellow and orange sponges, white and golden tunicates, wispy hydroids, rough mats of bryozoans and abundant psychedelic elegant anemones – the swell in these gullies causes a fairly constant flow of water, allowing such organisms to flourish.
These sedentary creatures live most of their lives in one spot, waiting for food to flow towards them. For photographers, it’s macro heaven.
Numerous mobile species also abound, including small spider-crabs decorated in yellow sponge; tiny but elaborate nudibranchs; large, healthy lobsters; red-eyed swimming crabs, always on guard; and swirls of saithe, swimming gracefully over and around the swaying kelp.
The relentless pendulum-like motion in these gullies, caused by the swell, makes it tricky to stop in one place for too long, let alone take photos.
Gripping on in a fight against the current presents a fun challenge, but the struggle soon becomes futile, and it’s easier simply to go with the flow.

NORTH RONA
After a decent night’s sleep and a substantial breakfast (cooked and served by Mary, our gracious hostess, deck-hand and general all-rounder) we got the news we were anxiously awaiting – the conditions were good for our attempt to strike out to the islands.
The North Atlantic swell was fairly forgiving for the five-hour crossing, and soon North Rona was looming on the horizon.
The island is steeped in history. It was inhabited, on and off, for 700 years, until the early 1900s. A small population survived on the island during the 1600s, but was wiped out after an infestation of rats, probably from a visiting ship, ate most of the island’s produce and possibly introduced the Plague.
North Rona was occasionally occupied by shepherds until the mid-1800s and was then largely uninhabited.
Continuously farmed by the folk of Lewis, nowadays North Rona is owned by Scottish Natural Heritage, which manages it as a nature reserve, primarily for its grey seal and seabird colonies.
The small, natural harbour on North Rona offers relatively good protection from the wind and swell, and is the best chance of a safe anchorage.
Each evening before the light faded we would go on deck and marvel at the cliffs towering above us, covered in seabirds in a constant state of motion, flying to and fro. Rafts of puffins sat on the water, with hundreds more flying in their typically frenzied fashion. Above them cruised the ever-graceful gannets.Although most of our dives would be around Sula Sgeir, we were able to do a few around North Rona.
Diving here is relatively easy and presents the classic scenery one would expect from a wild and exposed Scottish island – clear water, abundant healthy kelp, large boulders covered with pink encrusting algae and mussels, and frequent patches of colourful jewel, dahlia and elegant anemones.
A lasting memory of diving the kelp forests of North Rona will be the huge numbers of tiny but charming iridescent blue-rayed limpets clinging to the kelp fronds, and also the sheer number of snow-white and bright-yellow Polycera nudibranchs, at times forming clusters of 20 or more.

SULA SGEIR
Approaching Sula Sgeir, it is soon apparent how the island gets its name (sula is Gaelic for gannet and sgeir means rock). During the summer more than 8000 gannets crowd onto this small but spectacular island, making it one of the most important seabird sanctuaries in the UK.
Under water, the scenery is similar to North Rona’s, but with a more dramatic topography and greater diversity of species, many of which you would not expect to find in such extreme exposure.
The sheer cliff-faces that plunge directly into the cold, nutrient-rich waters provide the perfect habitat for a remarkable array of life.
Delicate nudibranchs cling onto algae that cover dense layers of barnacles and other sedentary species. Golden tunicates and beautiful iridescent Devonshire cup corals are scattered here and there. Invertebrate life is at times so dense that not a centimetre of bare rock can be seen.
The underwater landscape includes many gullies which, typically, become dominated by thousands of jewel anemones that line the walls to feed in the current. These anemones become so dense through a process known as “longitudinal fission”, whereby they stretch their base and split themselves
in two across the middle to produce two identical anemones of the same size.
The process takes only a few hours, and eventually creates huge patches of anemones of a single colour. These spread out, overlapping onto differently coloured colonies and resulting in sheets of bright luminous green turning to deep purple, bright orange, pink and all the colours in between. They rival coral reefs for vibrancy.
Sula Sgeir has a number of impressive caves and archways, many of which have rarely, if ever, been dived. These provide some of the most exhilarating diving, with surging currents and abundant, occasionally unusual, marine life.
A particularly impressive site, North Thamna Sgeir, includes a massive archway that leads through a large rock just off the north-east of Sula Sgeir.
The arch opens up like a black hole, its walls heavily lined from top to bottom with softly coloured orange and white plumose anemones. It drops down to 30m and forms the entrance to a large cave that leads right through the rock and out the other side.
The island is an important breeding habitat for grey seals, so encounters while diving Sula Sgeir are very likely. However, unlike better-known sites such as the Farne Islands, the seals here are unused to divers, and seem very cautious.
Apart from a couple of closer interactions we would mostly catch a glimpse of one or two seals in the gloom, or beneath us as we were ascending.
Each time we surfaced at Sula Sgeir, we were met by hundreds of gannets circling overhead, apparently curious about the numerous fluorescent SMBs that had popped up.
Watching them from the water while we waited for the Halton to pick us up created a sense of dizziness as they circled, at times coming just beyond arm’s reach to get a closer look.

THIS EXPEDITION WAS a reassuring affirmation that diving in UK waters can be just as spectacular and rewarding as in many of the far-flung tropical destinations so revered by divers.
These wild and exposed islands provide habitats for an astounding variety and abundance of marine life.
Places like these feel the more special because, although remote and hard to get to, they are a part of our heritage.
We were fortunate to be allowed a glimpse and privileged to be given the opportunity to report back on how remarkable UK diving can be. We hope to return in the future for more diving in the wake of the guga hunters.
Big thanks go to Paul Holmes for organising the trip and to Bob, Mary & Kenny of mv Halton for their experience, care and attention to detail. Thanks also to Seasearch and Chris Wood, for the help in supporting the expedition.

THE SEASEARCHERS
Seasearch was set up in the mid-1980s by the Marine Conservation Society to enable participating recreational divers to gather information on seabed habitats and marine life around the UK and Ireland.
Volunteer divers can undertake one- or two-day courses, with the option of further specialist courses in marine-life identification and survey techniques.
Seasearch data is collected carefully by buddy-pairs of divers. In its simple form it involves swimming slowly over the seabed, recording the habitat type and its associated marine life. When a new habitat is encountered the depth is recorded, and a list of species and a habitat sketch is made on a slate.
Often marine life is encountered that cannot be identified, so it helps to be able to take a picture to aid identification later.
Once the dive is over, all the information on the slate is transferred to standardised Seasearch forms. These are collated at the end of the expedition and posted to the national co-ordinator Chris Wood, although in this case he was on the trip.
The data is entered into Marine Recorder, a database used by the Joint Nature Conservation Committee (JNCC), Government conservation agencies and local biological record centres.
Seasearch data is all available to use and download from the National Biodiversity Network (www.searchnbn.net), with survey reports and more information at www.seasearch.org.uk