We sit expectantly, drifting on a deep, calm sea. Apart from the sound of the ripples gently slapping the side of our inflatable boat, all is quiet. The only movement comes from ospreys circling the distant, shimmering cliffs. Suddenly, a deep, mournful sound reverberates through the water. Far below, a humpback whale is singing.
"We think the humpbacks here are unique, partly because their song differs from other populations," whispers Fergus Kennedy, of Oman's Whale and Dolphin Research Group. "Only the males sing, so we know there's a male down there. We think it's associated with breeding."
We're spending a week on the Sanjeeda, a traditional sailing dhow of the kind that once carried cargoes of frankincense and spices across the Indian Ocean. The 93-ft boat has been chartered by Omantravel, which takes paying guests around the Arabian Sea. With two masts fashioned from whole tree trunks, long curved booms from which the sails hang, and a carved sea eagle at her prow, Sanjeeda looks like a pirate galleon. But her stability, high teak sides, and diving and snorkelling facilities make her an ideal - and stylish - vessel from which to observe Oman's marine wildlife.
Fergus and his partner, Anna McKibbin, are on board for the season to gather information on local cetaceans and share their knowledge with guests. These include a geologist, Roger Dixon, and his partner, Elaine Marjoram; housewife Mia Tod; Omantravel's director Margaret Wharton and her husband Mike; Alex Benwell, a photographer; and myself. Our captain is Nigel Godfrey, a tall, laid-back ex-military man who commands his seven-strong Indian crew with the help of Souku, a silent, wide-eyed sulphur-crested cockatiel.
We're exploring the five Al Hallaniyah islands, also known as the Kuria Murias, having motored north and east from Mirbat three days ago. Given to Queen Victoria in exchange for a snuff box, these exposed outcrops remain largely unvisited on account of their remote location and seasonally stormy waters. Their isolation has helped to make them a haven for wildlife of all kinds. We've seen 100-strong schools of frisking dolphins, black and white masked boobies, the occasional turtle, and now our singing humpback whale.
We keep our eyes peeled at all times for water spouts or fins breaking the millpond surface. When the cry of "whale breaching" or "dolphin ahoy" goes up, Fergus and Anna take detailed notes of the species, group composition and behaviour. If we spot a humpback they zip across the swell in the inflatable to photograph its tail fluke and dorsal fin for the research group's database. It turns out that our underwater crooner has been seen several times before and is called Smooch, on account of the kiss-shaped scar on the base of his dorsal fin.
Little is known about Oman's marine wildlife because of the country's extraordinary past. Between 1938 and 1970, Sultan Said bin Taimur maintained medieval-like conditions for his people while living in luxury. There were no hospitals, no schools, no shops and only 12km of tarmac road. Only after a coup in which Bin Taimur's son overthrew him were the first group of tourists allowed to visit, in 1983, but until very recently visitors were strictly policed. "When a sailing dhow entered Omani waters with tourists on board last year, everyone was arrested," says Margaret. "So we're lucky we got permission to be here."
We certainly feel lucky to be here. By our fourth day we've all adjusted to the rhythms of nature. We get up at 6.30am, when the sun comes up, and retire at 9pm, when the sky is inky black and the deck dimly lit with kerosene lamps. Most mornings there's time to jump into the cool brine for a leisurely swim round the boat before breakfast. Guided by the wind, waves and wildlife encounters, we travel for a few hours while the sun is at its most intense. Then we anchor in a sheltered bay. If there are a few daylight hours left, we go for a snorkel or dive, returning as Nagrash, Sanjeeda's shy steward, brings up steaming bowls of freshly made fish curry, chapati and rice for dinner on deck.
After mooring beside uninhabited As Sawda island, we don snorkels, masks and fins to explore the underwater world. Paddling through the water we spot needle-teethed moray eels in coral hidey-holes, shoals of pouting lemon thicklips, turquoise and mauve parrotfish and well-camouflaged mottled crocodile fish. And the show doesn't stop when we leave the water. Seconds after clambering back on board Sanjeeda, a six-ft shark-like creature winds its way languorously through the water from the stern, the white underbelly of a ray grasped in its jaws. Consultation with Sanjeeda's book on fish yields two possibilities. We've either been sharing our snorkelling patch with a harmless guitarfish - or a human-attacking sand tiger shark.
It seems we're only just getting to know the secrets of these alluring islands when its time to leave. We set out early, as Nigel is keen to make the most of the strong breeze by sailing. It's a far more complex procedure than on modern boats. First the ship must be positioned with the wind behind, so the sails fill as soon as they are unfurled. Then Gabriel, the sail-master, has to shin, harness-free, up the forward mast to release the jib-sheet. After a few moments of frantic hauling on ropes the billowing fabric is tamed and the sail set. Then the process is repeated for the main sail. For a full hour we enjoy the silence and gentle rocking motion until Nigel admits we've only travelled a mile. If we're to make the mainland we'll have to motor. We finally reach the coastline after dark and spend our last night moored in a deserted bay at Bandar Qinqari. Lying on the deck, watching the stars seemingly roll back and forth across the sky, and listening to the creaking of the rigging, it's easy to think back to the days when dhows regularly sailed these waters.
Tomorrow we'll be thrown back into the bustling modern world, but tonight we are experiencing Arabia as the frankincense and spice merchants did all those years ago. For one last night we're alone with the hidden creatures that inhabit the deep. The humpbacks are no longer singing but we know for sure that they're out there sharing rocky reefs and deep canyons with their cetacean compatriots.
GIVE ME THE FACTS
How to get there
Carolyn Fry travelled with Gulf Air (0870-777 1717; www.gulfairco.com), which offers return fares from Heathrow to Muscat from £330 return. Omantravel (01235-200 444; www.omantravel.uk.com) offers tailor-made itineraries in Oman from around £795 per person, based on two sharing, including return flights from Heathrow, transfers, five nights' b&b in Muscat and two nights as guests of the Omani family in the desert. Sanjeeda (01491-641 485; www.sanjeeda.co.uk) can accommodate up to 12 passengers and is available for private charters from around £1,000 per day fully crewed, on an all-inclusive basis.