DIVING ON AN EXTINCT volcano is all well and good, until you remember that sometimes volcanos erupt. And that, in fact, it was only six years ago, and just a short RIB-ride away, that another submarine volcano spewed molten lava and toxic gases into these waters off the southern coast of El Hierro, the smallest of the Canary Islands, for three months straight.
That eruption turned the sea an eerie shade of green, killed off all the marine life and caused the evacuation of La Restinga, the village where I’m staying.
Fortunately El Bajón, El Hierro’s most famous dive-site, is breathtaking enough to distract me from this worrying realisation. By the time I’ve dropped from the buoyline onto the top of the taller of the volcano’s two towers, swimming against a strong current alongside a massive shoal of zebra sea-bream, thoughts of floating lava bombs and toxic seas are far from my mind.
Pretty much the only thing going through my head at this point is: “Wow!”
The majority of La Restinga’s dive-sites are located quite close to shore, variations on a very enjoyable theme – sloping reef formed by the flow of lava into the sea at some stage in El Hierro’s ancient geological past, and myriad shallow caves.
The area is colonised by a huge number of marine species, from a rainbow of algae to zebra sea-bream, and visited, we’re told, by passing manta rays, whale sharks, dolphins and turtles in late summer and autumn.
The Mar de Las Calmas, which stretches westwards from La Restinga, is protected from the prevailing winds, meaning that even if it’s blowing a gale in the village (which it usually is) and your journey out is a bumpy one, the sea is almost always as flat as a pancake at the dive-sites on this side of the point.
El Bajón, however, is a different story. Located 555m offshore, in waters choppy enough to make me queasy, the volcano sits on the seabed at around 60m, its petite crater at around 20m and its towers rising to 6m and 9m.
Moray eels can be spotted all over the place, but not hidden in holes, as you might expect; at El Bajón they’re out in the open, loitering on algae-covered ledges and in the volcano’s crater.
Dusky grouper – some as big as bumper cars – roam the area, perfectly happy to let divers get up close to gawp, while arrowhead spider-crabs hang out in every crack and crevice.
A scribbled leatherjacket that appears right at the end of my dive gives me an absorbing safety stop.

AS YOU MAKE YOUR WAY AROUND the volcano you’re dealing with a different current situation every few minutes, a pleasant drift suddenly becoming a slog of a swim and vice versa.
It’s tiring, but exhilarating too – especially given the variety of marine life on display.
Life here is so plentiful partly because of the eruption in 2011/12 (locals report a massive increase in the number of fish compared to before the volcano did its thing) but also because the area is a protected marine reserve.
Fishing is tightly regulated. Only 12 divers are allowed on each of the 12 dive-sites within the reserve at any one time.
It gets busy here when the pelagics are in town, but on this off-season trip to
La Restinga my buddy and I have the place more or less to ourselves.
Two or three dive-boats go out each day, but most of the village’s 10 dive-centres are closed, and the boats that do go out are far from full.
While the other Canary Islands are major tourist destinations, El Hierro is hardly visited, meaning that the people who do make the effort to get here – almost all of whom are Spanish, mostly native Canary Islanders, in fact – come specifically for the diving.
La Restinga in January is a very quiet place indeed, which is just fine by me.
Marine life apart, the other big draw for divers is the geology of El Hierro’s volcanic coastline. My first dive of the trip is at the Cueva del Diablo (Devil’s Cave), a 15-minute boat-ride into the marine reserve past several miles of barren but beautiful lava-flow landscape.
The actual Cueva del Diablo is a large grotto in the cliff that people were once able to reach on foot. Since the many earthquakes that accompanied the 2011/12 eruption, however, it’s now accessible only from the water.
What you visit as a diver is a smaller – but still spacious – cave nearby, with a wide mouth that opens out to a sandy, boulder-covered seabed at about 8m.
It's home, like every dive-site here, to several trumpetfish and a generous sprinkling of yellow sponges. It’s an easy and enjoyable first dive, and would make a good first cavern-dive for beginners.

EVEN PRETTIER IS THE ARCH just outside the cave, which stands silhouetted against the bright blue of the shallow water.
There’s another gorgeous archway at El Tacarón, a dive-site a little way along the coast located just off the spectacular natural swimming pool that gives it its name. Descending a buoyline off the point, I follow my guide through a canyon of algae-covered lava before crossing the rocky seabed to return to the cliffs, where I poke my nose into the little caves that line the shore.
On the way I spot my first bull ray, a tantalising glimpse of what it must be like here when the megafauna come through in autumn.
I return to the pool at El Tacarón a few days later, spending the afternoon swimming in the chilly clear water (and very much feeling the cold after diving in a drysuit) and splashing around in rock-pools with my daughter.
While the island’s other swimming spots are at the mercy of fierce winter winds, this sheltered cove is swimmable every day of the year.
As afternoon turns to evening, we grill fresh fish on the public barbecue, before returning to La Restinga via the tortuous road through the volcanic badlands.
As far as post-diving excursions are concerned, El Tacarón is pretty much the only option, thanks to the extraordinary topography of El Hierro.
To get almost anywhere on the island, an extinct volcano the steep slopes of which drop straight into the sea, you have to go up and over, putting yourself at risk of decompression illness if you haven’t waited long enough after your last dive.
The single road out of La Restinga climbs to around 1200m over a distance of just 12 miles, with only the sleepy town of El Pinar at a low-enough altitude to be safe to visit if you’ve been diving that day.
So my partner Steve and I take turns to explore the island with our daughter on our non-scuba days. It works well for us because we’re tag-teaming diving and childcare anyway, but not everyone will be happy to be stuck in such a remote spot for the duration of their holiday.
With just a handful of restaurants, two supermarkets and a tiny beach, La Restinga gets boring fairly fast, especially when you consider that El Hierro offers some astonishingly beautiful drives, lovely walking trails through ancient forests and more than a dozen picturesque rocky bays and beaches for swimming. It’s an island you want to make time to explore.
Of the dive-sites close to shore in the Mar de Las Calmas, my favourites are El Salto and El Desierto.
Situated where the volcanic reef meets a “desert” of white sand stretching some six miles to the Punta de Orchilla,
El Desierto is home to what my guide, Iñaki Cayón from the Centro de Buceo El Hierro, claims is the largest population of garden eels in the world.

AFTER A SHORT SWIM from the buoy, our group lines up at the edge of a seemingly endless sand patch. Moments later the eels begin to emerge, coming further and further out of their holes as they get used to our presence. They stretch as far as the eye can see (which is around 30m, given the vis today), numbering in their thousands, if not tens of thousands.
Swimming over the sand patch to reach the reef is like playing an enormous, non-contact game of whack-a-mole – the eels disappear as you approach, only to come up again once you’ve passed on
Neighbouring El Salto is a wonderland of small, shallow caverns, beautifully lit from above by natural windows in the cliff. My two visits to the site – the first with a guide from a dive-centre that opened last year, the second with Iñaki, who’s been here since 2001 – make for
an object lesson in the importance of booking with an established operator.
Dive number one is perfectly enjoyable, but it’s on dive two that I’m shown the full extent of this magical site, and my photographer-buddy is given the time he needs, rather than being rushed along.
Iñaki also knows where the good stuff likes to hide, pointing out lots of marine life I would have otherwise missed, from porcupinefish at El Desierto to lobsters at El Río, a site just outside La Restinga’s harbour wall.
It’s too windy to dive outside the Mar de Las Calmas on all but a couple of days of my trip, but I’m glad of the dives I manage to squeeze in in this area.
El Río is all about the ravines, while at El Veril the lava platform ends in a sheer wall that makes this one of the most spectacular and dramatic dives of the trip.
It also happens to be the last, which is fortunate because as I pull my drysuit over my head, ready to walk the short distance back to the dive-centre from the harbour, the neck-seal rips.
It’s as if the suit has decided that I’ve seen enough here, and it’s time to go home. Having visited most of El Hierro’s dive-sites over the course of two weeks, including repeat visits to the best of the bunch, I’m inclined to agree.
But I’ll be back – if there’s one thing that beats diving on an extinct volcano, it would be seeing a manta ray while you’re at it. Bring on the autumn.