Most British divers have a dolphin story to tell, but not so many can recall diving with whales. Yet a surprising variety of whales feeds in our waters, or passes through them. Rico Oldfield has prepared this illustrated guide, so you'll know what to enter in your logbook when the unexpected happens.

The idea of crossing paths with one of the true giants of the deep is rarely at the forefront of a British diver's mind. But whales shop in the rich food market of Britain's territorial waters more often than you might think, and chance encounters can and do occur.
Although smaller cetaceans - dolphins and porpoises - commonly approach divers under water, it is rare for whales to venture so close. They are more likely to be seen first from your boat at some distance off. Moving closer by boat is not recommended: it can cause the animals stress, and may breach the Wildlife and Countryside Act.
If you're already in the water, however, a whale, even at ambling speed, will quickly be able to leave you in its wake. In this case, the whale will also have picked up your presence long before you noted his, and could have been long gone if he wished. This adds a special zest of mutual greeting to a whale encounter.
So what are the keys to spotting whales, and other cetaceans, at the surface; and what chance do you have of identifying exactly the animal you're looking at?
Prime territory for whale-watching is near land lying closest to the edge of the Continental Shelf, where the deep Atlantic Ocean comes up against the "shallows" of the European continent. Whales are spotted regularly off such places as the Western Isles and southern Ireland, where whale-watching boat charters have found a growing niche.
Chance encounters can, however, occur for diving parties afloat at any point around the British Isles, so it is worth keeping your eyes peeled wherever you may be.
Indeed it takes a sharp eye to spot a spouting whale, as it sends a jet of water skywards from the nostrils that nature has planted at the top of its head. And after the waterworks you are left with a challenge because, like an iceberg, only a small proportion of a whale's body may break the surface.
The dorsal profiles of different types of whale do, however, differ at least slightly. Get to know your fins, humps, bumps and swimming styles, and you have a chance of some successful detective work.

MINKE WHALE	HUMPBACK WHALE
FIN WHALE	RIGHT WHALE
BLUE WHALE	SPERM WHALE

Many of the smaller whales, such as pilot and killer whales, have a body architecture closer to the dolphin group than the large whales.
The pilot whale, at 6m or so long, swims like a dolphin, displaying at the surface a distinct "looping" motion that reveals its head and back above the sea. At some distance, too, it can be recognised by its unique "yacht-keel" dorsal fin, particularly pronounced in the male.
The pilot's round, blunt head has a slight beak and its flippers are long, slender blades. A lighter saddle mark can sometimes be seen on its black back behind the dorsal fin.
Pilot whales hunt for fish in huge pods, sometimes numbering hundreds, and wander close to the Atlantic seaboard, generally from June to September. They can, however, be spotted in the western Channel and northern North Sea between November and January.
The infamous killer whale has a reputation for attacking mammals such as sea-lions, smaller dolphins and, in packs, even other whales. It has also taken the blame for small boat sinkings in open ocean. Although such things have occurred, the killer whale is, for 99.9 per cent of the time, a humble fisherman hunting in packs of three to 30. It is most likely to be seen by divers inshore along the Atlantic seaboard and in the northern North Sea.
With a stout, piebald barrel body of 10m or more, the killer whale could be confused by the uninitiated for a very large pilot whale, the swimming motion of which it shares. It is, however, easily distinguished by an awesomely tall, pointed dorsal fin. And, if you are close enough, a white slash can be seen stretching along each side of its head from behind the mouth.

Other whales resembling large dolphins appear in British waters, but they can be hard to identify, even upon a stranding. Typical groupings are beaked and bottlenosed whales. Their dorsal fins, compared with dolphins', are set much nearer their tails, and their flukes do not feature the central notch that dolphins have.
Whales of the rorqual group are toothless browsers that use an extended bottom jaw to scoop small creatures from the surface of the sea. Those known to visit British waters include the humpback, fin, sei and giant blue whales; and, at the other end of the size scale, the little minke or piked whale.
Apart from the humpback, the rorquals can be quite difficult to tell apart. All have an even back carrying a small, curved fin set well towards the tail. Size will be the main pointer to which rorqual you are looking at.
The minke whale, small at around 9m long, is Britain's commonest inshore rorqual and has been the subject of marine conservation surveys off coasts including the Scottish Isles.
Apart from its size, the minke is characterised by its pectoral flippers which, in northern waters, bear a distinctive white bar; further south they can be completely white.
Keep your eyes peeled for this little whale along the Atlantic seaboard and in the northern North Sea, from May to October. Fairly secretive visitors among the larger rorquals are the fin whale and its slightly smaller cousin, the sei whale. On the surface they are nearly impossible to tell apart, for a 17m whale could be a small fin or a large sei! The large humpback whale, by comparison, is characterised clearly by its lumpy back. A deep-ocean animal, it is known to cruise in over deeper parts of the Continental Shelf between April and September. It can turn up, for instance, between Cornwall and the Scilly Isles, and off the coasts of Ireland and Scotland.
Despite being 20m or so in length, a quietly cruising adult humpback may be spotted only in reasonably calm conditions, for often all you can see are a few irregular humps on the top of its head and, some metres apart, another set of humps which adorn its back. The small rorqual dorsal fin, set well back on the body, will also be visible.
An altogether rarer experience would be to see a humpback turn gymnast, forget the burden of 35 tonnes of muscle and blubber, and try to fly. It can lift nearly its entire body clear of the water in a mighty leap.
By far the largest rorqual, however, is the awesome blue whale, which grows up to 55m long. Sadly, from hundreds of thousands thought to have roamed the oceans, only 5000 to 10,000 blues are believed to have survived the whale-hunters. Although they have been sighted offshore, understandably they are rare visitors. The other giant whale of possible relevance to British divers - and a more likely sighting around our coasts - is the mighty sperm whale. A toothed whale, it is perhaps the most easily identified. There is no dorsal fin, and a series of raised ridges show over halfway down its back and ripple down to its tail. This unique crest is obvious as it dives. Perhaps the sperm whale's best signature, however, is its spout. Forwardly directed through one nostril at the front of its head, the angled outrush is unique in the whale world.
Sperm whales swim in family pods in deep water offshore. But these compulsive wanderers can approach the coast from July to December and, every so often, surprise the crew of an inshore boat.

Whales of the rorqual group are toothless browsers that use an extended bottom jaw to scoop small creatures from the surface of the sea. Those known to visit British waters include (top to bottom) the humpback, the fin, the sei, the minke and (at back) the giant blue whale. The minke is Britain's commonest inshore rorqual.

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