BOBBING ABOUT METRES from the Cornish coastline, I slid over the side of the boat into the chilly water. The beasts I had come to see are known to be quite skittish, and could disappear at a moment’s notice.
Although notoriously hard to find, moments before, just 10m from the shore, we had caught tell-tale signs of our quarry.
I had come to see the UK’s largest native animals and the world’s second-largest fish – the basking sharks.
From April to September, Cetorhinus maximus can be spotted right along the west coast of Britain. The best places to see them are in Cornwall, off the Isle of Man and in Scotland, and there are a number of companies (panel overleaf) that can take you out shark-spotting and, if the conditions are right, offer the chance to swim with these leviathans.
Each year, the first shark sightings take place in the south-western corner of the UK, which was why I had come to sunny Cornwall. Heading out of Penzance harbour with expert basking shark spotter Charlie Hood, we had motored west along the coastline past Mousehole, and were now almost in sight of Land’s End.
I was out filming for an episode of Britain’s Secret Seas, the BBC’s follow-up to its acclaimed Oceans series, but set around the UK. In the boat was professional explorer and diver Paul Rose, marine biologist Tooni Mahto and newcomer to TV, underwater journalist Frank Pope. None of us had seen a basking shark before, let alone had the chance of swimming with them.
Growing up to 10m long and weighing in at around 7 tonnes (about the length and weight of a double-decker bus!), the basking shark is a seriously large fish.

FOR THE BEST CHANCE of spotting the sharks, you need calm waters and sunny weather. We had only enough cash to pay for a single outing, so there was a lot riding on us not just spotting a shark but successfully filming it under water in glorious hi-definition. Hugging the coast, with everyone’s eyes on the water, we had our fingers crossed.
Guided by reports from other skippers radioing through sightings, it wasn’t long before we spotted the tell-tale sign of our first shark, its caudal fin poking through the surface.
Due to the protected status of basking sharks, there are specific guidelines for manoeuvring your boat near and swimming with these wonderful fish (see panel, right).
We had decided to leave the scuba gear behind, because the bubbles are known to disturb the animals and they tend to swim off.
All the action happens in the shallows, so snorkelling is the order of the day.
Basking sharks can swim at up to 6 knots, so there is no point trying to keep up with them. The best strategy is to get dropped in ahead of the fish, float at the surface and watch them as they swim by.
Patiently we waited in the water. Seconds turned into minutes but then, with cameras running, out of the gloom loomed two gigantic sharks, their 1.5m mouths wide open, their vast tails silently pushing them through the water.
More accustomed to underwater archaeology, Frank was aghast at their sheer scale: “That was so much bigger than I was expecting,” he said.
We had by now been joined by five or six more sharks, and Charlie was impressed: “I was hoping to see one basking shark, but to be surrounded by 10 is pretty spectacular!” he said.
Never one to be lost for words, Paul found it “hard to believe that these things live in British waters.” Tooni, too, was amazed: “I kept looking up at the shore and thinking, this is Cornwall. This is unbelievable”.
So what’s so special about our West Coast waters that they draw in these big sharks Despite the clear blue sky and gorgeous sunshine, the water was quite murky. This is because we were swimming in a thick living soup of the sharks’ food.
Unlike their razor-toothed predatory cousins, these colossal fish are filter-feeders, eating microscopic plankton, and the west of the UK juts out into the north Atlantic, catching currents that bring the nutrients that fuel plankton-blooms.
Even with the knowledge that these colossal beasts pose no danger to us, Paul found it quite unnerving to swim so close to them. “It’s quite something to have a mouth that big, stretching over 1.5m across, coming at you!” he said.
The sharks simply swim along with their mouths agape to catch the plankton on their modified gill-rakers, and they can filter a volume of water equivalent to an Olympic-sized pool every hour.
As a giant tail-fin passed powerfully past my head, I found it ironic that one of the largest animals in the sea feeds on some of the smallest.
Little is known about the full life-cycle of basking sharks, nor about their global health as a species.
To understand more, a couple of months later, we found ourselves off the coast of the Isle of Man in the Irish Sea, in the care of Jackie and Graham Hall of the Manx Basking Shark Watch.
“These are big, beautiful, charismatic creatures,” said Graham, with a wistful look in his eye. “They fill you with enthusiasm and passion,” chipped in Jackie. Clearly we were in the company of confirmed shark-lovers.
Using a catalogue of photographed dorsal fins, each bearing a unique set of nicks and cuts, these eagle-eyed spotters can identify specific individuals from day to day and year to year.
As part of their monitoring work, Jackie and Graham are also involved in a worldwide project to try to assess the global genetic health of the species.
They hope to reveal any breeding patterns between isolated populations, and even estimate the total number of basking sharks in the worldwide population. To do this they need to take a DNA sample from each shark, which is quite a tricky prospect – solved in an ingenious yet simple manner.
We found shark-spotting off the coast of the Isle of Man a lot harder than in Cornwall, with a floating log in the shape of a dorsal fin fooling us not once but twice.
Fortunately, a couple of hours in and we finally caught sight of a shark.
Not quite the gigantic specimens we had seen down in Cornwall, but a shark all the same.
Approaching very slowly, Graham took to the bow holding his home-made DNA sampling device – a pole with a kitchen scourer attached to the end.

WITH JACKIE INCHING the boat forward, Graham leaned over and gently rubbed the scourer on the shark’s dorsal fin. What comes off is a sort of black “goo”, an oily substance that coats its skin, but also containing skin cells that contain DNA. The sample was sent off to the lab for analysis.
With DNA data coming in from shark-watchers around the world, plus GPS tracking information from tagged sharks, scientists are just starting to unravel their mysterious life-cycle.
Jackie was pleased with the results so far: “It seems that at least some individuals are going on long migrations to breed. This will give a mixing of the genes and help maintain a healthy and robust gene pool,” she said.
On a more localised note, Jackie and Graham regularly spot and catalogue many small sharks, measuring around 1.5 to 1.8m long.
“We have far more newborn sharks in this 25-mile stretch than in the whole of the rest of Britain,” I was told. “If they’re not being born here, they’re being born very close by.”
It’s possible that the Isle of Man is a basking-shark nursery, or even a birthing ground. “They don’t just come here to feed, but also to breed,” said Jackie.
If you get a chance to swim with these gentle giants this summer, I couldn’t recommend it enough. It’s wonderful that Britain is home to such giants, and great that they eat only plankton!

Because of their endangered status, basking sharks are protected under the Wildlife & Countryside Act (1981), the Countryside & Rights of Way Act (2000), the Northern Ireland Wildlife Order (1985) and the Nature Conservation (Scotland) Act (2004). These acts make it illegal to intentionally kill, injure or recklessly disturb or harass the sharks in British waters.

To reduce the risk of injury or disturbance, the Shark Trust and the Marine Conservation Society have come up with the following guidelines:

* Do not try to touch the sharks.
* Maintain a distance of at least 4m from each shark, and be wary of the tail.
* Groups of swimmers should stay together and ideally remain at the surface.
* Restrict the number of people in the water at any one time.
* Avoid flash photography, which can scare the sharks.
* Do not use underwater propelled devices.

* Restrict your speed to below 6 knots, and avoid sudden speed changes.
* When closer than 100m, switch the engine to neutral to avoid injuring sharks.
* The viewing distance between the boat and large groups or courting sharks should be at least 500m.
* Be extremely cautious in areas where basking sharks have been seen breaching.
* For every shark visible on the surface, there are likely to be more hidden just below.

Most operators who can arrange spotting or swimming with basking sharks work by taking names and contact details of prospective clients.
Once sharks have been spotted in their areas, they contact those clients a day before a planned outing. The season runs from April to September.
Prices for snorkelling trips vary considerably. The RIB Logan charterboat in Cornwall costs £250 to charter for the first hour, then £50 an hour (£75 at weekends), plus VAT.
It takes up to seven passengers, though four snorkellers with camera gear is the maximum. Individual places cost £150 where available.
Isle Of Man Diving Holidays offers four-day trips with B&B accommodation and eight boat outings for the same price as its dive packages – £300pp.
In Scotland, Acuatours claims to be the only company to offer a dedicated week-long trip to snorkel with and photograph basking sharks in the UK, and also to have the best sighting rates. With land-based lodgings in Tobermory and non-basking-shark diving also available, it costs £865pp.

CORNWALL (April-September)
RIB Logan, Penzance,
Atlantic Diver, Newquay,
Shearwater II, Penzance,

ISLE OF MAN (June-September)
Isle of Man Diving Holidays,

SCOTLAND (June-September,
peak mid-June to mid-July)
Acuatours, Tobermory,

Further information