I looked out across Poole Harbour, searching for the dolphin as directed by the local old salt. I could see no sign of a marine mammal with a smile.
As it turned out, in that part of the world anything sticking out of the water - in this case a wooden post - is called a dolphin. Still, here and elsewhere the living creatures are common enough.
There are between 31 and 45 known species of dolphin and other small toothed whales, depending on how you group them. They inhabit all the temperate and tropical seas.
The common dolphin is as widely found as its name implies, and is a familiar sight in the Mediterranean. Its black back, contrasting with its ochre and grey flanks, makes it among the prettiest of the small whales and it has been celebrated in art since ancient times.
The Atlantic bottlenose is one of the largest dolphins, unless you include orcas, pilots and false killer whales. Worldwide, however, travelling divers are more likely to see pan-tropical spotted and spinner dolphins in the wild. These are well-named and can be observed swimming at the surface on almost every passage by boat in the tropics.
When the liveaboard mv Lady Jenny V plied the Eritrean and Sudanese Red Sea, she was often greeted in the morning when the sea was calm by thousands of spinner and spotted dolphins, joyfully taking turns to ride the pressure wave at the bow. The world seemed full of dolphins.
While the passengers excitedly clapped their hands or whistled, or hurriedly donned their snorkelling gear, the crew, too long at sea and tired of humouring client-divers, would jokingly tell them they would have more fun with a shotgun. Only for effect, of course.
Vessels of all sizes attract dolphins. In Mallorca I have come across large common dolphins cavorting at the front of a small inflatable, which can be quite a nerve-wracking experience.
The four most commonly encountered dolphin species each have a pronounced beak, or rostrum. This is not a nose. Like all whales, dolphins breathe through a blow-hole in the top of their heads.
They have tiny ears, which they probably use only when their heads are out of the water. Their underwater acoustic sense and echo-location skills are legendary. The sound-generation within the bulbous foreheads is sophisticated enough to give them a clear picture of their surroundings.
Dolphins are mammals and as such are warm-blooded and bear live young, which they suckle. They have always had a special relationship with man, perhaps because they like to come up and take a cheeky look into our world - or is it because of that permanent smile
Why do they smile A dolphin is a mammal and as such needs fresh water, which it gets from the fish it eats by swallowing them whole, using its teeth merely for gripping. Inevitably it takes in a gulp of seawater with its lunging bite, so the rear of the mouth is used to eject the seawater squashed up by its tongue.
Perhaps we have an affinity with dolphins because they breathe air like us and spend a lot of time swimming near the surface. Alone among sea-dwellers, it is whales and dolphins which reveal their presence when they breathe.
Because of this, they were a lot less mysterious to ancient peoples than other creatures of the deep, and healing powers were attributed to them.
Stories of dolphins rescuing drowning people predate Flipper by many centuries and there have been many accounts of dolphins preferring the company of humans to that of their own kind.
For all these reasons, there is probably no creature with which people want to dive more. So where can you do it
First of all, it is important to note that swimming with dolphins in blue water has its risks. Jeremy Stafford-Deitsch wont forget the time he dropped in with a huge pod, only to discover an equally huge school of at least 100 grey reef, silky and silvertip sharks below them, ready to clear up the mess of wounded fish that had escaped the dolphins - or, indeed, to pick off any wounded or sick dolphins.
Splashing about at the surface, involuntarily doing an impression of a sick or wounded mammal, will invite a speedy response from these predators, and possibly an investigative bite.
The sharks rushed up to meet Jeremy. He does not recommend the experience.
Eye for the ladies
Wild dolphin encounters under water tend to be fleeting for scuba-divers. Often you hear the characteristic whistles and clicks rather than see the creatures, and if you find yourself momentarily within a passing pod you can count yourself lucky. The social grouping of dolphins does not normally include noisy, air-gushing divers.
There are places, however, which have become associated with diving dolphin encounters. Bimini in the Bahamas has a pod of wild spotted dolphins which do not seem to mind divers (see below).
JoJo is a male dolphin which became an icon for Providenciales in the Turks & Caicos Islands - that is, until he started becoming too amorous with the occasional long-haired female diver. As one witness told me: Goodness, Ive never seen anything like it! JoJo is an oddball, a social outcast dolphin that sought friendship with man - one in particular, Dean Bernal from California - instead of his own kind.
There are other examples. A female spotted dolphin (below) has buddied up with a young deaf-mute Bedouin man at the village of Mezzina, in the Egyptian Sinai, south of Nuweiba. Abdullah and his family have turned their friendship into a useful additional source of income and you can pay to either scuba or snorkel with the unlikely partnership.
This dolphin, Oline, has mated with passing wild males, but sadly none of her offspring have survived for long. She still prefers the company of her man-friend.
Around Britain and Ireland, the same phenomenon of the lone dolphin has occurred. After seeing his young son lifted out of the water by one known as Donald in the Isle of Man in 1974, Dr Horace Dobbs gave up his career as a research scientist to swim and scuba with dolphins, to study them, write books and lecture on the subject.
He attributes healing and therapeutic properties to dolphins and reckons that clinically depressed people who get the opportunity to enjoy a close encounter with them benefit from the experience.
Donald went on to become a well-known character in the waters off, in turn, Ireland, Wales and Cornwall.
Another solitary dolphin, which lived off Godrevy Island near St Ives between 1981 and 1984, was Percy. He became something of a celebrity and a tourist attraction, though fame eventually went to his head, and he became aggressive and started exhibiting indiscriminate sexual behaviour.
He was reported as attacking a windsurfer, and caused rifts among the locals, who had different ideas about how to treat him.
The following winter, Percy vanished. But Fungie, another man-friendly dolphin, still frequents Dingle Bay in south-west Ireland. And a Rissos dolphin, a stout-bodied species without a pronounced beak, is regularly sighted off the Welsh coast.
What is obvious is that these solitary dolphins are in no way normal. Most are male, and their affinity to man might be considered an aberration that is not necessarily entirely healthy.
Like captive dolphins, these individuals can become sexually precocious. One hapless diver was involved in a legal action when he was witnessed by a boatload of dolphin-watchers apparently doing something indecent with Freddie, a friendly dolphin which frequented the area near Amble, in Northumberland.
Horace Dobbs testified in court that it was more likely the male dolphin trying to do something indecent to the diver, and a not guilty verdict was recorded.
Dolphins have a very large, fibrous penis (another reason for that enigmatic smile) which is held within the sheath, or prepuce, inside the body until it becomes erect. As Dr Dobbs told me recently: I thought everyone knew - all these male dolphins do that! Embarrassed by the incident, Freddie has since decided to relocate.
So much for individuals - what about groups Scientific studies have found that some dolphins form very large groups, while others live in groups of only a few. Some have an extreme range, others live in more restricted zones.
In Florida there is a closed bay with a resident pod of about 100 animals, all living within about 80sq km. They show no signs of interacting with other dolphins outside their restricted ambit.
A bunch of friendly bottlenose dolphins live in Moray Firth, but a decision has been made not to publicise their existence, for their own protection.
But at Sanctuary Bay, Freeport, Grand Bahama, a colony of Atlantic bottlenose dolphins lives side by side with people. Originally rescued from dolphinariums and film projects (one, called Cocoon, was featured in the film of the same name) they have since bred, and their children enjoy the slightly unnatural lifestyle of rehabilitated prisoners.
Atlantic bottlenose dolphins are among the best-known to the public, from appearances in films and dolphinariums. This sub-species is readily adaptable to captivity, so it is also the type most likely to be in need of rescue. It is not indigenous to the Bahamas.
The natural lifespan of bottlenoses approaches 40 years, and these ones have taken to a life in which they are free to escape but have no natural prey. They find it far more convenient to return to Sanctuary Bay to eat imported north Atlantic fish than to hunt the sub-tropical variety, which dont simply jump into their mouths.
The major concern at the Sanctuary Bay dolphin encounter, run by Dolphin Experience, is to give non-swimmers a close-up interaction. This is inevitably rather formal and orchestrated. The more adventurous can spend time in groups of six, frolicking with a couple of dolphins within the confines of the bay, but scuba-divers can enjoy close encounters with a selected pair of younger animals that will follow their trainers boat out into the open ocean.
The encounter is limited not by the dolphins abilities but those of the paying audience. It involves stroking, playing with a small hoop, spinning divers about their own axis and kissing, for those brave enough to do it.
All this still smacks of the dolphinarium, though the trainers would prefer to change things. If only we had more competent divers, they confided to me.
Walking the dogs
Every day the trainers escort the dolphins out to sea without an audience: walking the dogs, so to speak. I was privileged on one occasion to accompany a mature female called Robala, the mother superior - the senior dolphin of the resident pod.
Robala has been known to go out in the open ocean to search for and escort back recently arrived Sanctuary Bay dolphins that have lost their way home. A massive animal of around 4m long, with an extremely tough hide, she was full of personality. It was a bit like being in the company of a very experienced local diver!
She would spiral away towards the surface at speed, disappear through it for a breath of air, then hurtle back towards me, stopping precisely where she had been a few moments before. I found the whole process impressive but daunting.
Another place to experience a controlled encounter is Dolphin Reef in Eilat, Israel. The dolphins live in a large netted enclosure which allows smaller wild animals to pass through from the sea.
Divers can pay for an encounter but the venue is always well booked, and I have noticed the dolphins getting bored after the first group of divers of the day.
More than 40,000 visitors a year visit Monkey Mia at Sharks Bay in Western Australia, where wild bottlenose dolphins have made it a habit to voluntarily strand themselves to meet people!
Monkey Mia is thought to be named after HMS Monkey and the aborigine word moa, or home. Its dolphins are the only wild herd in the world to have befriended humans in this way. First noticed back in 1964, they have become a big tourist attraction, but the dolphins seem unconcerned for the moment.
Wherever you are, should you encounter a pod by chance, enter the water quietly one by one as the boat makes a wide circle. The dolphins will come close to the luckier members of the group. Swimming and splashing will disturb the mammals and increase the risk of unwelcome shark interest in you.