LOOKING UP TOWARDS THE SUNLIT SURFACE, I could see the nitrox bottle drifting down towards us. Swimming over to it and grabbing one of the regs, I settled in for a few minutes of deco - as usual, slightly more than we had intended, Bernard having got a bit carried away chasing that last sample.
Judging by his gestures, he was pleased with the 15 we had collected. The sun was out, my drysuit hadn't leaked and guillemots were providing entertainment for the stop, diving down towards our bubbles. Another good day's work.
It may not have crossed your mind while diving that there could be undiscovered marine species just metres away. Those small, brightly coloured patches you brushed past on the way into the wreck may be intricate things of beauty never recorded in the annals of science.
They could help to warn us of environmental problems; some may even hold a cure to cancer. Yet, until now, most people have ignored them.
During 2005 we discovered an incredible 28 new marine species on a six-week diving expedition. No, not in the clear waters of the Caribbean or remotest Borneo but right on our doorstep, on a small island called Rathlin, sandwiched between Scotland and Northern Ireland at the top of the Irish Sea. Working on the project was fascinating.

I LIKE TO TELL PEOPLE that I work as a sponge diver (especially in front of my mother, who despairs of me ever having a 'proper career'), but in fact I work as a marine biologist for the Ulster Museum in Northern Ireland.
Bernard Picton, my boss, is Curator of Marine Invertebrates. He led four trips to Rathlin over summer 2005 in which I headed off, with the rest of the museum team, to research its sponges.
You might be surprised by how many naturalists work behind the scenes at museums, organising trips to find new material for collections, and contributing to the understanding of the field. It's a contrast to the idea that museums are just somewhere to go on emissions of noxious chemicals.
In his quest for sea slugs, Bernard developed a keen interest in sponges, but soon realised that they deserved some study in their own right.
Even among marine biologists, sponges have a reputation as being difficult to identify. Early workers in the field couldn't even decide whether they were animals or plants. The last time they were seriously researched was the 19th and early 20th centuries, the Victorians having a soft spot for them.
Most sampling then was by dredging up boulders from the seabed, so many species are known only from tiny preserved fragments. Before our recent project we had no idea of what many species, even quite common ones, looked like when alive.
Say 'sponge' and most people conjure up an image of soft bath sponges (or, at a push, Spongebob Squarepants). In fact they come in a huge variety of forms and colours.
The 'spongin' tissue that makes up the main body of this invertebrate is usually supported by a skeleton of 'spicules', hard structures of calcium or silica. These come in many shapes, some strikingly beautiful under a microscope. Use one of these in the bath and it would cut you to shreds!
It is possible to identify a few species under water, such as the familiar large grey mound of the elephant's hide sponge, Pachymatisma johnstonia, but most of our sponge species form thin crusts that can at first look nondescript.
These flat sponges can range from about 1cm to more than 20cm across. Some are so thin that it's almost impossible to scrape them off the rock, causing much swearing when we tried to sample them (luckily we weren't using voice comms!).
It can be hard at first even seeing such small patches, or telling them apart from other encrusting species such as bryozoans. Our highly scientific method for telling them apart is that, when poked with a pencil, a sponge is spongy and a bryozoan hard.
After a while, however, our eyes became accustomed to the subtle differences between the species, some having amazing patterns.
We named the yellow crust Hymedesmia stellifera after the star-shaped veins on its surface. I think it looks like loud '70s wallpaper, but I couldn't work out the Latin for that.
We were trying to collect as many of these crusts as possible to get a complete record of Rathlin sponges.
To identify the crust-forming species, we collect them by scraping a small piece from the rock (swearing optional) and pickling it in alcohol, examining the spicules and skeleton under a microscope back in the laboratory.
Because the waters are so clear on Rathlin the kelp goes down to 20m-plus, and red weeds to around 30m.
Sponges tend to be best below the algal zone, so we dived mainly in 30-40m to try to escape the weed. This resulted in restricted dive times, so we had to work fast. We aimed to keep deco time to 10 minutes, limiting bottom time to around 20 minutes.
We took three photos of any likely suspect. Given the sponges' diminutive size, this required a 60mm macro lens.
Bernard and I both use housed Nikon D70 digital cameras (mine in an Ikelite housing and his in a Subal - he gets paid more than me!).
Sponges are similar throughout, so we needed only a small piece to identify the beastie. Using a knife we scraped a small sample into a bag. Sounds simple, but opening small Ziplock bags under water is a knack (gloves were soon abandoned).
The currents had a habit of whisking away samples, and often we were forced to pursue an escaping piece of sponge in the vain hope of scooping it into its bag.

SO WHAT CAN SPONGES DO FOR US that justifies all this effort? They are an important part of many marine communities, particularly on cliffs and other rocky areas. They feed on miniscule particles that otherwise would not get back into the food chain, and a host of predators such as sea slugs and crabs then feed on them.
Sponges also provide a home for other smaller animals, either on their surface or within their tissues, where the water chambers make cosy burrows.
In one study, 11 species of sponge from one area were found to have 242 other invertebrate species living in them.
The number of sponge species present can help to indicate how healthy an area is, and increases in numbers of particular species may even provide early warning of pollution, temperature changes due to climate change and other types of environmental problems.
Scientists are also starting to realise the potential that chemicals produced by sponges, for protection and defence, have for use as drugs.
These 'bio-active' compounds have been successfully developed into new antibiotics and anti-cancer drugs, but so far most of this work has been done in the tropics. Recent studies revealed that a very common British shore species
had anti-cancer potential, and the team believes that many more compounds could be discovered from British sponge species.
Rathlin, a small island six miles off the north coast of Northern Ireland, is six miles long, and just over 100 people live there. The population has risen as high as 1000 but has fluctuated, with unlucky inhabitants massacred by a series of Viking, Scots and English invaders.
Being almost midway between Scotland and Ireland goes some way to explaining both Rathlin's strategic and biological importance. The narrow 13-mile gap at the top of the Irish Sea funnels through vast quantities of water with every tidal cycle. Situated in the middle of the North Channel, Rathlin is exposed to the full force, resulting in very strong tidal streams, up to eight knots at spring tides in some places.
The gushing water carries plenty of food, the tiny planktonic plants and animals providing sustenance for a dense cover of filter-feeding animals such as anemones, hydroids, soft corals, bryozoans and, of course, sponges.

ONE OF THE MOST DIFFICULT ASPECTS of dive-planning was choosing sampling times. Very localised eddies often set up against the main tidal streams, making it difficult to predict slack times.
On the relatively flat east coast, missing slack results in an exciting drift dive, but on the steep cliffs of the north wall it could result in a current pulling you down to 200m.
We tried to dive all around the coast of Rathlin, but in some areas the tides confounded us. We didn't manage to sample the north-east corner of the island, where the notorious MacDonnell Race forms standing waves for much of the tidal cycle.
We often used shotlines to assess tidal conditions, and as a precaution all dive pairs carried EPIRBs (beacons that could signal our location to the emergency services) in case of surface separation from the dive boat.
When we did hit slack, diving conditions were often excellent, with visibility sometimes exceeding 15m.
Rathlin's three main areas are the north wall, the east coast and the southern bays and slopes.
Dropping over the cliff edge and down the sheer north wall, you are faced with a mass of colour: white and yellow trumpet anemones, dead men's fingers and sponges. In good vis you can see the wall looming off beneath you (a sight that has induced vertigo in some of my dive buddies) and it is tempting to keep following it down.
If you know where to look, a series of limestone caves and arches, popular with local divers, can be found. The larger arch makes an easy swimthrough, and is spectacular when viewed from beneath on a sunny day, with the clearer surface water framed inside it.
On the underside of the arch you'll find tiny dead men's fingers, the rare species Alcyonium hibernicum known from only a few sites around the UK. These have a delicate pastel pink fluffy surface, almost as if knitted in angora.
Just around the corner we found a gully covered in large patches of bright yellow sponge, giving the impression that someone had decorated it badly after watching one too many DIY SOSs.
This also turned out to be a new species - we called it Spongosorites calcicola, (limestone-loving), as we found it only on this sort of rock.

THE EAST COAST IS A MUCH MORE gradual slope, mainly of sand and gravel. The main sites of interest to us in this otherwise rather barren, tide-swept area were the Lochgarry wreck and a small bedrock reef about halfway up the coast.
The Lochgarry is a friendly wreck, sitting upright usually with good vis and large shoals of pollack around its upper decks. Unnoticed by wreckies, its surface has many sponge patches.
We discovered the reef by accident
on our echo-sounder while waiting for some decompressing divers to surface. Bernard dispatched the next pair for an experimental dive to investigate (this usually means it's my turn to go in!).
It was worth it. We discovered a steep blocky bedrock reef, decorated with a fringe of delicate lacy hydroids, the faces in-between being Sponge City.
Some of my favourite sites were on the south coast, in particular a small bay tucked under Black Head. The steep boulder slope here is dotted with many bright yellow sponges resembling scrunched-up dusters (Axinella damicornis).
We called this Damicornis Bay, as we couldn't find a local name for it.
It was hard to concentrate on the sponges here. Octopuses were common and willing to pose for photos.
Large colonies of the football seasquirt Diazona violacea were also present, glowing like weird alien lifeforms, and the potato crisp bryozoan Pentapora foliacea was abundant.
All Rathlin's sites have much to offer anyone with even a passing interest in marine life - even those who aren't sponge nerds. You can dive it from the nearest Northern Ireland mainland town, Ballycastle, but being based on Rathlin was much handier.
We would often work long hours, and being on site meant we could check the diving conditions by gazing over the
bay over breakfast. Rathlin also seems blessed with a sunnier microclimate than the mainland. In Northern Ireland, you take your sun where you can get it.
Of the 128 sponge species we found, 28 were new, three others had never been recorded in the UK, and nine more were new to Northern Ireland. We are still working on 19 more species, and think some are also new to science.
We now have a much better idea about UK sponges, and think we have found all these new ones mainly because nobody has sampled in this habitat and depth range before.
Sampling by scuba-diving was great, because it let us sample small patches and get good images of the species (and that's not just an excuse to get more dives in!). We hope to go on to collect sponges from more sites in Scotland and Wales. Conveniently, they like tideswept areas with spectacular scenery, which should mean more great diving.
So where has this project left me? As a bit of a Johnny-no-mates, it seems!
I was already a keen underwater photographer, and apparently there's only one thing worse than a buddy who is a photographer, and that's a sponge-obsessed photographer constantly looking out for new species. My buddies don't appreciate spending most of a dive staring at a 'massive' 5cm sponge patch.
So, erm, I'm looking for new buddies with more sympathy for my new-found enthusiasm. Up for a dive, anyone?