Diving the Isle of Man: The Booroo

by Bill Sanderson

The Isle of Man boasts a dramatic cliff strewn coastline broken by long golden beaches. The waters are a clear rich blue, nurturing teeming communities of plants and animals. Brightly coloured fish follow divers hoping for easy food. The sun sets not over the Mediterranean or the Pacific Ocean, but over the Irish Sea! The palm trees outside Ronaldsway airport on the island always serve to reinforce an incongruous tropical image which the temperate waters betray. To us however; hardened (dry-suited!) divers, the cool seas of this largely undiscovered diving destination were a minor consideration against the thrilling dives which awaited us.

Janolus cristatus nudibranch, Isle of Man. Copyright Tim Nicholson
Janolus cristatus nudibranch. Photo credit: Tim Nicholson

Off the south-western extremity of the Isle of Man is an amazing diving area called the Calf of Man and jutting off the southern extremity of the Calf is a tremendous dive site called the Burroo. The Burroo and the isolated isle, the 'Calf' are steeped in history and legend and almost exude atmosphere. At a little more than one and a half miles at its widest, and with a total area of only six hundred acres, the craggy Calf has supported in its time; the world's largest population of Manx shearwaters (some many thousands); a population of over thirty farm workers; various hermits; light house keepers; shipwrecked sailors; mythical pirates; a monk and a mischievous collection of fairies!

Seal, Isle of Man. Copyright Tim Nicholson
Grey Seal. Photo credit: Tim Nicholson

The whole south west area of the Isle of Man, and notably the Burroo, is without doubt a special place for marine life. Below the waves and beyond the view of many, the intricate rocky coastal topography extends into the alluring depths. This variable terrain, in conjunction with very strong tidal forces, has created a myriad of different marine habitats resulting in a concentrated feast of life that is a microcosm of Manx marine life as a whole. This pristine part of Manx coastal waters is so unique and attractive that it has become highly regarded amongst all those who dive here. In order to ensure that the spectacular marine life survives, the Calf area has been designated as a Marine Nature Reserve.

The intriguing name of the Burroo, we have discovered, almost certainly came with the Vikings, derived from the Scandinavian word borg, meaning small round hill. This is not really very surprising, since the Isle of Man has been invaded by just about everybody in it's time, galvanising a strong sense of independence and self government in the modern Manxman. Neither the name, nor the bountiful and extremely striking marine life at this dive site are easily forgotten.

Polycera quadralineata nudibranch, Isle of Man. Copyright Tim Nicholson
Polycera quadralineata nudibranch. Photo credit: Tim Nicholson

On the south side of the Burroo the main cliff face continues underwater into a short vertical drop and then becomes a bedrock slope. At around 15 m this provided a good, sheltered entry point. However, the Burroo, possibly once the site of some Nordic defences, is now-a-days renowned as a favourite nesting place for many timid seabirds in the summer season. These include guillemots (Uria aalge) and razorbills (Alca torda) and as we entered the water we had to be careful not to disturb the birds. From the base of these underwater cliffs a rocky incline with intermittent large bedrock mounds and boulders could be seen running off into depths in the 40's to the south and west. We followed the precipitous flanks of the outer rock in spectacular 15 - 20m vis past a couple of large bowl-shaped gullies, one of which is referred to as 'the amphitheatre'. Trapped at the base of one of the small underwater faces in this area was a huge timber, no doubt from a ship, and possibly part of one of the many unknown wrecks in this part of the Irish Sea.

Tidal streams off the Burroo are amongst the most severe around the Isle of Man. Strong overfalls, up currents and eddies are commonplace, and on a calm day at full flood we have watched the waters appear to boil; this is definitely a slack water dive! As the sea plies tumultuously around the exposed rocky promontory, animals living in this current swept environment receive a deluge of suspended, planktonic organisms from the passing water. This forms an abundant food source for a dazzling multitude of 'suspension-feeding' animals that proliferate here in the gullies and on the flanks of the underwater cliff faces.

Plumose anemone, Isle of Man. Copyright Tim Nicholson
Plumose anemone. Photo credit: Tim Nicholson

The majority of these 'suspension feeders' are invertebrates with particular adaptations to suit the location. They are characteristically anchored or cemented to the underlying bedrock, with tentacles or tiny projections to draw or seize their food from the passing water. The oaten-pipe hydroid (Tubularia indivisa) is of this design, upholstering boulders and bedrock to give a soft velvety appearance. Similarly, anemones such as the striking and aptly named jewel anemone (Corynactis viridis) form massive patchwork quilts of incredibly vivid and diverse colours. These tiny animals, like other anemones, can multiply by splitting (cloning), producing identically coloured neighbours. Abutting one patch of copy-cats may be other patches of individuals of completely different colour forms, producing mind-boggling mosaic patterns on the rock. Elsewhere, abundant sponge mounds appear to have oozed like toothpaste from the rock.

Anemones and hydroids, Isle of Man. Copyright Tim Nicholson
Jewel Anemones and Hydroids. Photo credit: Tim Nicholson

Of course, there is also a multitude of predators and scavengers to be found in this 'outerspace' seascape. The edible crab (Cancer pagurus) is one of a number of conspicuous crustaceans here, roaming almost undisturbed in its bulky armour. Velvet swimming crabs (Necora puber) with their acid red eyes can be seen in abundance, scurrying in aggressive retreat. A great multitude of sea slugs graze their way through the wall to wall shag-pile carpet of hydroids during the summer months, adding more startling colour detail to the softened outlines of the rock. A recent marine biological survey found an amazing 56 such species around the Calf! It is not uncommon when diving here to find shoaling fish such as pollack (Pollachius pollachius) or 'callig' in Manx. Towards the end of our dive we had found ourselves immersed in a great living cloud of these shimmering forms as we ascended the short 15 m underwater cliffs on the southern flank of the outer rock. The Burroo is also a common haul-out site for members of the resident Calf seal colony. We had seen inquisitive grey seals (Halichoerus grypus) basking at the surface which through their curiosity had come to cryptically escorted us through our dive like a body guard; always there in the background somewhere!

Anemones and hydroids, Isle of Man. Copyright Tim Nicholson
Pollack or Callig. Photo credit: Tim Nicholson

The Burroo, with its extremely diverse and plentiful marine life offers a truly magnificent dive. In fact, in areas exposed to the fast flow, it is something of a challenge to find a single square centimetre of bare bedrock, so abundant is the life here. We can only agree with the numerous experienced divers, underwater photographers and marine biologists who repeatedly acclaim it to be one of the best in the British Isles. (For those who feel inspired to dive some of the most spectacular and as yet largely undiscovered marine life sites in Britain, more information has is available through a book by IMMEL publications entitled Dive sites and marine life of the Calf of Man and neighbouring area). By Bill Sanderson, Bruce McGregor, Andy Brierley and Rupert Lewis.

The author of this article wrote Dive Sites and Marine Life of the Calf of Man which you can buy from Amazon.co.uk. Dive Isle of Man