|SHARK attack behaviour|
The upset shark pushes its pectoral fins downward and moves erratically. (You have the chance to swim away and avoid).
The back is arched and the movement becomes exaggerated, with the head moving from side to side. (You still have a chance to escape unharmed, but it doesn't take long to reach phase three.)
Seeing no other way out, the shark charges, often with a bite. (Ouch, you pushed it too far).
| SHARK bites|
In 1808, a basking shark washed up on the Isle of Stronsa was reported to be a sea snake with a mane like a horse and six separate feet.
Hammerhead sharks have long been the fascination of scientists trying to fathom the development of the head. Popular consensus now recognises that it probably gives the shark lift and lessens the energy output required to swim.
There are approximately 350 species of shark and only a handful are known to have attacked people.
The whale shark is the largest fish in the seas and can reach more than 14m in length.
Most sharks must move to pass water over their gills and to maintain depth - unlike fish, they have no swim-bladders. Bottom-dwelling sharks, however, have the ability to pump water, allowing them to stay still for extended periods.
Sharks' sensory organs are very advanced and little understood. They have the usual sight, smell and touch, but also the ability to detect electrical signals, thanks to organs known as the ampullae of Lorenzini.
Reproduction in all shark species is slow. Relatively few young are born, some in eggs, others live. In some sharks, the sand tiger for example, the first-born devour younger siblings while still in the womb.