On the south side of Burroo, the main cliff face extends underwater to form a short vertical drop, before turning into a bedrock slope. At around 15m, this provides a good, sheltered entry point. Go easy, though: in the summer, Burroo is a favourite nesting place for many timid seabirds, including guillemots (Uria aalge) and razorbills (Alca torda), and it's important not to disturb them.

From the base of the underwater cliffs, a rocky incline with large bedrock mounds and boulders can be seen running off into the depths to the south and west. Follow the precipitous flanks of the outer rock past a couple of large, bowl-shaped gullies, one of which is known as the Amphitheatre. You may well spot a huge timber around here, no doubt from a ship, and possibly from one of the many unknown wrecks in this part of the Irish Sea.

Tidal streams off Burroo are among 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, the multitude of suspension-feeding animals that proliferate here in the gullies and on the flanks of the underwater cliff faces receive a deluge of suspended, planktonic organisms.

The majority of these suspension feeders are invertebrates that have adapted to suit the location. Anchored or cemented to the underlying bedrock, they use their tentacles or tiny projections to draw food from the passing water. The oaten-pipe hydroid (Tubularia indivisa) is of this design, and can be found upholstering bedrock, giving it a soft, velvety appearance.

The striking and aptly named jewel anemone (Corynactis viridis) can be seen here, forming massive patchwork quilts of incredibly vivid and diverse colours. Like other anemones, it multiplies by splitting and cloning, to produce identically coloured neighbours. Get several different types together and a mind-boggling mosaic pattern is the result. Elsewhere, abundant sponge mounds appear to have oozed like toothpaste from the rock.

There is also a multitude of predators and scavengers. Conspicuous crustaceans include the edible crab (Cancer pagurus), roaming almost undisturbed in its bulky armour, and the red-eyed velvet swimming crab (Necora puber). Sea slugs graze their way through the wall-to-wall carpet of hydroids that, during the summer months, adds yet more startling colour to the rocks. A recent marine biological survey found an amazing 56 such species around the Calf!

It is not unusual to find shoaling fish such as pollack (Pollachius pollachius) - known as 'callig' in Manx. Towards the end of one dive at Burroo, my buddies and I were immersed in a great cloud of these shimmering creatures as we made our final ascent on the southern flank of the outer rock.

Burroo is also a common haul-out site for members of the resident Calf seal colony, and inquisitive grey seals (Halichoerus grypus) have been known to escort divers through the water like personal bodyguards. Burroo is a truly magnificent dive site - it is something of a challenge to find a single square centimetre of bare bedrock, so abundant is the life here - and it lives up to its reputation as one of the best dive sites in the British Isles.