DECIDING WHERE TO DIVE on St Kilda is both easy and difficult. Easy, because one of the divers has brought along the small but detailed guide-book from Gordon Ridley’s 1980s expeditions.
Difficult, because Gordon Ridley has described so many enticing dives that we are spoilt for choice.
It’s a lazy morning in Village Bay. Resting at anchor after an overnight crossing, we breakfast while watching the clouds blanketing the peaks of Oiseval and Conachar, 294m and 428m above sea level respectively.
Not that we can see more than halfway up before they disappear. It’s a grey day with a tantalising promise of sunshine. More importantly, and somewhat unusually for St Kilda, there is barely any wind, a force 1 on the Beaufort scale from the south-east.
Various fast day-trip boats arrive from the Outer Hebrides with hikers and twitchers on board, drop anchor and decant their passengers to the jetty by tender.
It took Wandrin’ Star just under three days to get here from West Wales. With the majority of three weeks ahead of us, we’re in no hurry.
We could stay for a week or more if the conditions hold out, though we would be on hard rations by then.
With rations in mind, a few divers go ashore to let the island warden and ranger staff know our plans, and to scrounge some bread. Everywhere in the Outer Hebrides seemed to have sold out as we came through yesterday.
As well as being the westernmost part of the British Isles (apart from Rockall), St Kilda is home to the westernmost radar-tracking station for the Benbecula missile range from the Outer Hebrides.
As a World Heritage site, the island is not the actual target, and there were no range safety warnings on the VHF as we made the crossing, but checking in with the range is good form.

OTHER REASONS TO GO ASHORE would be to climb the mountains to admire the view and birds, or to visit the Puff-Inn pub. Alas, the sub-contracted civilian operators of the range station closed their pub to visitors a few years ago, allegedly under some excuse about security, or health and safety.
Even if it was open, the sun has yet to cross the yardarm. As for the mountains, they are still in the clouds. Climbing will have to wait.
I am among those who stay on board with binoculars and guide-book, admiring the scenery with a particular eye for Dun, the long knife-edge ridge of an island that protects the south flank of the anchorage in Village Bay.
I try to match up each of the cracks and caves with notes in the book. It follows the format of the old editions of the DIVER guides to Scotland, very precise and easy to follow if you have an Ordnance Survey map and can work in OS grid references. We have a marine chart and work in latitude and longitude, so locations such as NF109972 are not particularly easy to translate into reality.
Of course, numerous websites could do this for us, but basic mobile-phone coverage is patchy even in the Outer Hebrides, and St Kilda is well out of coverage. Perhaps when the radar station closes Vodafone can take over the dome and replace it with a cellphone mast.
The anchor comes up, and we head out to Dun. Like St Kilda, the scale of the big scenery makes it appear close, but what looks like touching distance takes a good 10 minutes by boat.
Back to dive-site location and, with vague memories from those of us who have been here before, we think we have located the entrance to the Saw Cut.
Above water, it’s a wobbly vertical fissure in the rock that gives just a shadowed hint of opening up below. Failing that, Dun Arch shows daylight through the island only a short distance further back.
Not knowing what shallow rocks could be lurking below the cliff, we use the tender to get close enough to dive. The water is blue, and so clear that the kelp reaches deep, but only on the upper faces of the rocks.
The lower faces are either bare or tightly packed with anemones.
Anywhere else, this wall and rocky slope would be a fantastic dive in itself. Here it is merely a prelude to the narrow cut that, as I cross a saddle in the rocks, opens into the heart of Dun.
The cut stretches from the surface down to 25m or more. It’s difficult to judge, because it continues further out as an open gully strewn with boulders, but my attention is focused inwards.
Nearly parallel walls vary from just far enough apart for one diver to fit, to just about wide enough for two dives to pass without bumping.

MARINE LIFE APPEARS in varying patches, but there is no bare rock. Near the entrance, yellow dead men’s fingers and brightly coloured anemones and sponges are obvious, but between these what from a distance look like plain brown patches turn out to be tightly packed tunicates or fuzzy bryozoans.
Further into the cut, the balance shifts subtly, with more sponges and tunicates.
It is only right at the back, some 50 or 60m in, that any bare rock shows. Here the walls are scoured by rocks tumbled by surging waves, though not today, as the sea outside is smooth.
With the guide-book written before dive computers existed, when most divers had a single cylinder with 10 or 12 litres of air, that would be about it.
Now we all have computers, and at least 15-litre cylinders, if not twin-sets or rebreathers. Dives can be much longer and Dun Arch is just along to the east, so I may as well enjoy two dives in one.
After a few minutes following along the wall, the cut of my second destination opens. It’s only 15m deep, and, looking up, I can see the shadow of the arch above.
Being longer than it’s high or wide, it’s more of a tunnel than an arch, though if we tend to think of tunnels as narrow, I can’t get both sides into a photograph here, as I could in the Saw Cut.
As I work my way through, I am aware of a gentle current pushing behind me. I turn regularly to make sure that I can get back against it.
With the other entrance exposed to the south, big waves must pound all the way through on all but the calmest days.
Even today, I get a subconscious feeling for the energy of the site. Clues such as the current, a barely perceptible surge and tightly packed anemones on the walls throughout hint at conditions that would be deadly in a big sea.
Back on the north side of Dun, I swim far enough along from the arch as to be out of the current before surfacing.

THE OTHERS ARE ALREADY BACK aboard Wandrin’ Star, swapping over for the next dive. With enough divers to man the boat and the tender, and plenty of duration left in my rebreather, I am not needed to help on the surface. Successful trips to St Kilda are rare, so
I must get as much diving in as possible.
After a 15-minute break, I drop back in at the entrance to the Saw Cut. This time, after a brief swim in and out, I head the other way and deeper, into a forest of enormous boulders beneath Dun Head.
Here the thrill is in winding through caves and tunnels beneath the boulders, where they are held up from the seabed or nestled against one another. The jewel anemones are as vibrant as on the previous dive. In deeper water and out of the surge zone, plumose anemones grow to their full size. The water is still predominantly blue, but a hint of green creeps in when I look up from 35m.
The rather late lunchtime conversation revolves around our next dive. The ridge of Dun points off to the south-east where, a few miles away, the blocky shape of Levenish squats.
Twelve years ago, on a previous trip to St Kilda, the longest tunnel I had explored was the Letterbox, a submerged slot less than a metre wide that passes through the middle of Levenish. It was a good job it was narrow, because there was so much surge we had to wedge elbows and knees, and my flashgun arms had been flapping in the breeze.
Today I suspect that it would be much easier. There is also the lure of more boulder caves in which to play, deeper below Levenish.
Six miles to the north, Boreray and Stac Lee are puffing a stream of clouds against the now-blue sky, reminding us of St Kilda’s volcanic origins 60 million years ago. It is the varied hardness of the different volcanic rocks that has led to seams of softer rock being eroded, creating the caves and tunnels that dominate the diving.
Directly in front of Boreray is Sgarbhstac, which at 28m high is an unimpressive rock compared to the 384m Boreray, or the monolithic Stac Lee, towering 175m high to the west.
Stac Lee has the big wall and a small cave, but Sgarbhstac has the hidden and unique feature of a massive submerged arch, one big enough to drive several buses through side by side, or even a skilfully steered submarine. Previous visitors rate Sgarbhstac Arch as St Kilda’s “must do” dive, so we decide to save it up for a day out at Boreray tomorrow.
Meanwhile, the perfect surface conditions may allow us to dive on the exposed west side of the main islands of Hirta and Soay, to eye up other possible sites, and to evaluate Glen Bay as an alternative anchorage.

AT THE NORTH-WEST CORNER of Soay, the pyramid-shaped stack of Am Plastair is exceptionally exposed, even by St Kilda standards. A tunnel runs through it from north to south, from 25m to just below the surface.
Even on a flat-calm afternoon with no perceptible groundswell, we can easily pick out which cracks in the rock expand into the tunnel entrance.
Some divers were dragged through and knocked unconscious back in 1983, and this leads to some circling of Am Plastair and consideration before we decide to give it a go.
I plan to start on the wall outside and near the bottom of the tunnel, to poke my head round the corner to see what it’s like, and to check that I can turn back before committing to each stage.
The diving begins more easily than expected. Outside the tunnel there is little surge. I head for 20m and pause at the first obvious corner marking the entrance, poking my head round it.
Unlike the Saw Cut, the entrance is cut diagonally, and is a funnel shape.
It’s the sort of situation that could lure a diver in past the point of no return as the groundswell surges through. Still, I feel happy to look a bit further.
The lower slope of the entrance is lightly peppered with round scour-holes, perfectly circular pits in the rock, with a few pebbles at the bottom. Crabs seem to like them as hiding places, but I wonder where these crabs go when the sea builds up and the pebbles start rattling round.
The opposite side of the tunnel slopes overhead and closes in. The floor is a 1m-wide strip of gravel and small rocks, sloping upwards to complete the funnel shape. Above, I can see the darkening of the roof, but cautiously elect to stay about three-quarters of the way down.
A gentle surge is now perceptible, so I check again that retreat is possible before edging forwards. We are now definitely into the tunnel, rather than playing about in the entrance.
The sides continue to narrow in, while the whole aspect of the tunnel twists closer to upright. The roof is beginning to show some definition. Perhaps if I had a high-powered technical dive light I would be able to pick out more.
As it stands, a dive light is not necessary, I can see blue from both ends of the tunnel. The bottom is now a tight V, where a crab is wedged firmly in place. I suppose it’s a safer home than the scour-holes, but I still don’t fancy its chances in a storm.
The surge gathers strength, but we can still float in it safely without having to wedge ourselves in. It is only as the roof breaks the surface at the far end and the floor steps up that I sense that I have reached a line of no return.
From here, we could still go back.
Any further will be a commitment to go all the way through.

ONLY 10 METRES DEEP, I make a partial oxygen flush of my rebreather.
I have been keeping it on low set point and flying manual all through, but don’t want the electronics trying to take over as I flip myself up and over the last lip.
Now is also the time to dump as much buoyancy as possible. There won’t be time to play with drysuit or loop volume through the next few seconds.
I judge the surge and let myself go, kicking hard over the lip. I almost make it on the first wave, but have to grab and wedge just short of the far side.
On the next wave I make it, down beneath the southern entrance to the calm water of the wall outside.
Without having to protect my camera it would have been easy enough. On the other hand, even without a camera I wouldn’t fancy doing it on a rough day.
Back in Village Bay, the wind picks up overnight. By morning the waves are rolling into the bay, and our anchor is starting to drag. We get a weather update from a passing cruise ship, and it doesn’t look good.
Having got here all the way from Fishguard, a big decision is upon us – to wait it out in Glen Bay, or to make a run for it
A few failed attempts to get an anchor to hold in Glen Bay makes the decision for us. We clear the deck, batten down the hatches and head back to Harris. Our plans for Sgarbhstac, Levenish and more exploration are ended.
A few days later, as we continue to wait out the gale in Tarbert, we agree that it was definitely the right decision.

Wandrin’ Star doesnt run commercial trips to St Kilda, though if you want to dive from the boat in Pembrokeshire, visit – for St Kilda, see the classified ad pages.