Max Pugh takes the plunge on a holiday that sinks to new depths but offers a memorable wildlife experience
Mark Groves's underwater "safaris" operate in the warm (by British standards) and clear waters off the Isles of Scilly, diving or snorkelling with a group of grey Atlantic seals - big beasts, up to 8ft long. Because seal hunting has been banned for more than 100 years in the Scillies, the local seals are not quite as shy as they are elsewhere around the British coast - some flee when they see your boat coming, but others find you intensely interesting, and swim up for a closer look. The local Scilly divers have spent several years cultivating the trust of the herd, the result being that you can swim, quite literally, into their midst. Although seals can be aggressive on land, both from territorial instinct and fear of predators, underwater they change to playful, gently mischievous creatures - at least here they do. According to the locals, in three years of tourists swimming with the seal herd no one has yet been bitten.

You don't need any previous diving experience, only to be a good, strong swimmer, preferably familiar with using a snorkel and flippers. While waiting for low water, the safest time for swimming with the seals, Mark takes you through an initial briefing and, if necessary, a snorkel training session. Then you climb into a wetsuit, grab a weight belt and travel by power-boat to the seal feeding grounds. Despite their rather lumpen appearance when lying on rocks, seals are incredibly graceful, athletic swimmers and this particular group, well used to people, will show you just how graceful they can be, carving sweeping arabesques and circles around you as you hover on the surface.

If you have a BASC or PADI diving certificate, Mark will supply you with aqualung and regulator and you can go down deeper with the herd, following them along the sheer sides of the rocks. There are few wild animals to be found anywhere that will actually interact with humans. Perhaps for this reason, playing with the seals in their natural element sends you straight back to a child-like state of wonder. For the time that you are in the water with them, nothing else disturbs your mind.

If you have more than just a weekend to spare, or want to dive farther afield, Mark also leads dives to the scores of local wrecks, some of which are more or less intact - cannons, skulls and all. These deeper dives take in local coral reefs (yes, Britain does have them), basking sharks and deep marine life - such as angler fish, which attract other fish to them by means of an electric light growing out of their head - and occasionally blue sharks and thresher sharks. These trips are only open to those holding diving licences. If you do have one, you might be lucky enough to arrive when the migratory dolphin pods are coming through, providing an experience even more intense than swimming with the seals. However, you may or may not be allowed to go in with the dolphins - not all dolphins play gentle and there are risks involved, especially in the open water: they may decide to play for longer than you can stand, and they're much bigger than you are. So if the dive leader says no, respect his judgement.

The diving safaris can last from one day to six days. You stay in a local bed and breakfast, being picked up each morning, taken to the dive site, then delivered back in the evening. Try to allow time for at least three dives, whether you are just snorkelling or exploring the farther reefs and waters: the experience is addictive and the more times you go in, the more you will get to know the individual members of the seal herd. Once is just not enough.


Basics Island Underwater Safaris, "Nowhere", Old Town, St Mary's, Isles of Scilly, Cornwall, TR21 ONH, Tel: 01720 422732 Accommodation Mark will book local accommodation, from camping to hotels. Safety Instructor trained in first aid and dive rescue.Staff are qualified PADI instructors .

Season From Easter to October. Children All ages welcome, but only those over 12 may swim with the seals. Insurance Guests should provide holiday insurance. Tariffs Diving safari (includes instruction and equipment) pounds 28; pounds 128 for 6 days. Booking: 20 per cent deposit required. Access: From Penzance to St Mary's is a 20 minute helicopter ride - costs pounds 89 return. Flights leave every hour from about 7.30am (tel 01736 64296). Mark will pick you up on arrival.