Card size: 160x160mm. Blank inside.

Photography: Brandon Cole, Gavin Parsons (DB104, DB112, BD118), Rob Lind (BD105), Paul Tixier (BD106), Tony Sutton (DB108), Ben Hall (BD110), Peter Cairns (BD116), David Tipling (BD119, BD120), Mark Hamblin (BD121, BD124), Tim Laman (BD122)

Common seals are smaller, rounder and often regarded as ‘cuter’ than other British seal species. Almost feline in their features, with spotted coats and long whiskers, these marine mammals are certainly affable in nature. But images can often be deceiving, as behind that snout lies a sharp set of teeth, capable of pulling even the most tenacious lobster out of its rocky reef retreat. 

Common seals prefer to haul themselves out onto the more secluded and sheltered rocky shores and intertidal sandbanks. Strong swimmers, with powerful flippers and streamlined bodies, these seals can often be seen leaping (or ‘porpoising’) out of the water and can dive to great depths. Carefree gymnastics aside, there is some concern among marine biologists that common seals are in decline, being at risk from climate change and inshore pollution. Their protection under the EU Habitats Directive is important, not only for the seals as top predators but also for the lower levels of the food chain that underpins them and which they, in turn, control. 

Anthias share the same descent as predatory species of fish such as bass and grouper, but these colourful fish are the much more placid inhabitants of the coral reef. Huge shoals of these rainbow reef fish can be found surrounding coral outcrops, looking for plankton and small invertebrates to graze on. Their technicolour variety and peaceful nature means this family of fish are often collected for aquarium display; however, keeping any saltwater fish in captivity is not without its problems.  

Unlike hard corals, soft corals do not produce calcium carbonate exoskeletons and therefore do not build reefs. Within the feathery forms of these colonial animals, dwell tiny plant plankters called zooxanthellae. These microscopic plants produce energy for the corals via their photosynthesis and, in return, gain sanctuary among the coral’s stinging tentacles. With many other micro meals either sticking to, or floating by, the coral reef, it is easy to see why any self-respecting reef fish might find this a fine place to float. 

The striped marlin is a warm-water species found mainly in the Pacific and Indian Oceans. Reaching up to 3 metres in length, this elegant predator is a member of the billfishes – identifiable by their sword-like beaks. This appendage is actually an extended upper jaw, forming a rounded spear, used for defence and capturing prey items such as squid and crustaceans. Small shoals of marlin are also the marine masters of ‘bait balling’ fish – working as a team to condense a shoal of prey fish into a ball shape, with smooth swipes of their swords.  

Smaller than the blue marlin, these striped counterparts are recognised by their steely blue back adorned with cobalt stripes. This colouration is a great example of ‘counter shading’ – a highly efficient adaptation to a marine existence. Look down upon it and the dark back blends in with the deep. Look up at it and the white belly merges into the sky. And with nothing to fear except man, these formidable fish would otherwise live care free. Like all billfish, however, marlin have been intensively fished in recent years and conservationists are now giving them their due consideration. 

Although common seals are more feline, grey seals, with their long snouts, wide nostrils and bark-like calls, are comparatively more canine in appearance. Cute and fluffy they may be as pups, the big and burly adults are undoubtedly formidable. Dining on a range of fare including fish and shellfish, seals are opportunists. 

Britain supports more than half the global grey seal population, found dotted around its rocky shores in relatively remote locations. Hauling themselves out at low tide to bask, groom and loaf on the land, individual seals can be identified by their unique spot patterns. The best time to see them on mainland UK beaches is between May and October, with pups born mainly in late autumn and early winter.

The evolution of the wing-like head of these cartilaginous fish remains an eternal puzzle for the marine biologist. Indeed, the possession of this crown-like headpiece makes the hammerhead the most highly evolved of the shark species. Part sensory organ, part navigational compass, part weapon, the ‘hammer’ is thought to house a bank of electromagnetic receptors. 

Tropical waters and warm, temperate seas are home to eight species of hammerhead, each with a different hammer shape. In the case of the scalloped hammerhead, the leading edge forms a uniquely beautiful arc. Small groups of this predatory fish can be found gathering near seamounts, in deep water, pursuing shoals of fish. Hammerheads enjoy a diet mainly of bony fish, supplemented by squid and some smaller sharks. For the diver, however, these notably shy-and-retiring sharks remain a challenge to approach. Indeed, as climates change and waters warm, these sharks will stay deeper – and climate phenomena, such as El Niño in the southern Pacific, will only step up the visual challenge for the diver.  

Slick and streamlined in both personality and appearance, these mighty marine mammals hail from the cool waters off the rocky coast of western North America. Behind that cheeky grin and boisterous bark lies a most intelligent and social animal.  Known to congregate in large groups, Californian sea lions are renowned for not only their playfulness but also their performance of some pretty advanced social behaviour. Often referred to as the ‘walking seal’, the sea lion family have two most obvious features that set them apart from these close relatives: small cartilaginous ears and large flippers that they use to ‘walk’ with on land. 

Fair to say, the coolness factor is unavoidable with these guys – they have even been known to ‘surf’ breaking waves! Although populations of sea lions did decline in the 19th and 20th centuries, due to exploitation, pollution and disease, these anthropomorphic mammals are, thankfully, now on the increase.