ONLY 10 YEARS AGO, the idea of a swimmer snorkelling down to investigate a large species of unknown shark would still have been considered an act of suicidal lunacy.
Since that time, however, the effort to endear us to a beautiful and endangered group of animals has apparently disarmed us to their innocent but still potentially dangerous natures.
A news item in last Augusts DIVER galvanised in me a long-term concern. That June, a group were snorkelling in the Red Sea. A woman reportedly swam down to investigate a large shark the group were observing. She did not survive the interaction.
The species involved was Carcharhinus longimanus, the oceanic whitetip. Jacques Cousteau described it as the most dangerous of all sharks and many experienced observers, myself included, share this view.

UNTIL THE INVENTION OF AN OCEAN-SIZED LABORATORY, research into free-roaming wild animals like sharks must be based on field observation.
This is the sketchiest of research techniques, but even sketchy research will, given time, start to expose patterns.
The pattern I want to share with any diver who fancies the adventure of a shark encounter is this: of possibly 500 species of shark, four stand out head and pectoral fins above the rest as market-leaders in unprovoked attack. These are the great white, tiger shark, bull and oceanic whitetip.
To know and recognise any of these four fishes, and to be aware of their psychology, might be a life-saving factor in the compelling experience of shark encounter.
Most species of shark have been reported as having attacked humans at one time or another, apparently even the toothless basking shark! Most of these reported aggressions have, however, been provoked in some way.
A large but harmless nurse shark I encountered in a holding tank in Florida once tried to swallow my head and camera housing - it was just used to being hand-fed!
To disturb or molest a wild creature in its comfort zone often teaches us a painful lesson in respect for private space. To be fair to sharks, even a ladybird can bite! One of the big dividing lines between the vast majority of the shark nation and my four select species is unprovoked attack.
Divers and swimmers have shared the sea harmlessly with all four sharks, yet they have also shown that the rare chance exists for sudden and unprovoked attack, and these same four dont nip, they usually bite for keeps!
I dont want to deter anyone from the magic of a shark encounter; I want to ensure that you make risk assessments in the case of certain species, and based on a position of knowledge.
From the resources of the Museum of Florida comes the International Shark Attack File, probably the most referenced source of information on the subject. It advises caution
when interpreting its statistics.
Most of the data comes from shallow-water attacks, and from witness testimony. Most sharks look similar when viewed from the surface, and any witness would be high on perception-warping adrenaline.
Nonetheless, records have been coming in for so long now that strong patterns are emerging. The most dramatic concerns the four species I mentioned, which is why it seems
to be common sense to be able to pick them out.The great white shark, Carcaradon carcharias, is the largest-known carnivorous fish. Weighing up to 2240kg and reaching to 6m in length, only a very specialised minority would consider swimming unprotected with it.
The tiger shark, Galeocerdo cuveri, is mostly a darkness hunter but commonly patrols shallow water in temperate and tropical oceans. People have swum harmlessly with this species but it is a very powerful shark, known to spin around surprisingly quickly.
At up to 7.5m and 635kg in weight, wide escape windows are advisable.
The name comes from the striped pattern shown most vividly in younger specimens. Its jaws are powerful enough to bite right through sea-turtle shell.
So many man-made items such as vehicle number-plates and pieces of old tyre have been found inside this shark that it has earned the nickname garbage can of the seas! Its easy to recognise.
Not far behind the tiger shark in frequency of unprovoked attacks is the bull shark, Carcharhinus leucas.
Sometimes known as the Zambezi, as it is commonly found in fresh water, scientists once thought a shark found in Lake Nicaragua was a separate species until bull sharks were seen salmon-leaping over rapids to reach the lake.
They have been found thousands of miles up the Amazon river.

THE MOST ACCUSED OFFENDER for freshwater attacks, the bull shark measures up to 3.4m long and weighs up to 635kg. Deep-bodied and grey-coloured, it has sometimes been mistaken for the more docile lemon shark - often a painful mistake.
These sharks have earned attention-grabbing epithets - great, tiger, bull- but the oceanic whitetip bears a deceptively benign name.
Although behind the great white in ISAF shallow-water incident numbers, this species is widely believed to be behind a number of famous marine tragedies.
The torpedoing of the USS Indianapolis in July 1945 left a lot of people in the water. An estimated 60 to 80 sailors were reportedly killed by sharks. A similar fate befell the steamship Nova Scotia. Of the 1000 aboard, only 192 survived, with shark attack again the reported factor. Many authorities now believe a probable prime suspect was longimanus, and on this scale its way ahead of the great white in human attack statistics.
The oceanic whitetip is easy to identify and worth the effort. The name longimanus comes from its extremely long pectoral fins - it means long-handed. The dorsal fin is noticeably paddle-shaped, and without the infamous sinister recurve of the other Carcharhinidae. Each large fin and tail is conspicuously white-tipped.
The species could be mistaken for the relatively predictable silvertip reef shark Carcharhinus albimarginatus, but attention to those main fins will soon differentiate the two.
Normally a slow swimmer, longimanus is capable of great bursts of speed. Bold and fearless, it will approach swimmers in deeper water.
It has been known to attack unpredictably, without the investigation passes of other species.
This wide-ranging deep open-ocean shark has been recorded as far north as Gullmar fjord in Sweden, although it prefers warmer waters. Boat safaris put divers and swimmers far enough offshore to increase the chance of meeting it. Once estimated as the most abundant large animal on earth, indiscriminate fisheries are blamed
for a drastic reduction in population.
Such evidence of human pressure on any species endears us more to it, and focuses our conservation energies.
Such endearment is fine, but should not disarm us concerning the reality of its wild nature. Our own preservation must not conflict with its conservation!
Divers soon learn that most things under water are best considered untouchable. Rocks are coated with sharp barnacles worm shells; coral can sting and lacerate.
Most sharks can be considered completely approachable within known territorial boundaries but still untouchable.
My belief is that if more shark-encounter adventurers knew better how to identify and understand my four top untouchables, the International Shark Attack File would soon reveal a downturn.
And being alert and wary of just four species leaves hundreds of more sociable species with which to interact.
The victims of air and sea disasters who find themselves in the water with sharks do so involuntarily, but the shark-encounter experience is completely voluntary. We have the ability to understand the nature and behavioural characteristics of sharks; they do not.
In this context, I believe we can find the final defence of the shark. If ignorance is a voluntary misfortune, and someone approaches a dangerous animal ignorant of its nature, then isnt the resultant unprovoked attack just the result of the most blind and clumsy form of provocation