Most fatal collisions of man with bull shark was not in the sea and in fresh waters. Bull sharks inhabit, for example, in the lake Nicaragua. The Spaniards who first discovered this lake, located between the coast of the Caribbean sea and the Pacific ocean, found a small length of only 1.8 meters — sharks, which soon acquired a reputation as an extremely dangerous predators often attack people. It seems to me there is something particularly sinister in that, even bathing in the river or lake, away from the ocean waves, you suddenly find that you have aimed shark mouth.
Lake Nicaragua and the Caribbean sea joins the San Juan river, at the mouth of which also live bull shark. However, they seem not to be mixed with the lake sharks, although it is natural to assume that the bull shark is the descendants of the river, when rising up from the mouth, into the lake.
The African Zambezi river can also boast of the population of sharks not far behind her in that sense and some of the river Gambia. The Zambezi flows into the Indian ocean, the Gambia is located on the Atlantic coast of Africa. And in the Zambezi, and in the rivers of Gambia sharks are found sometimes hundreds of miles from ocean shores. It is possible that sharks inhabiting the African rivers, blockierten roundnose sharks. In relationship with them are probably sharks inhabiting the Ganges; and although they are small in size, but sent to the other world a lot of people. Asian rivers also caught sharks, very similar to the above-mentioned river types. Found in rivers and oceanic sharks in the Amazon, for example, and quite far from the mouth. Saw them in Tigre and Euphrates, and in the rivers of Southeast Asia and Australia. Some scientists believe that the ability of some shark species to adapt and to sea and to fresh water indicates that the origin of the shark dates back to freshwater species; however, while this is only Theorie .
In close relationship with margarinovyi are sharks and several species of hammerhead (Sphyrna); head of the shark is indeed like a hammer. Several unusual appearance has created a shark-a hammer more sinister reputation than this fish deserves. Larger species are hammerhead sharks really attack people, but this happens very rarely.
On the other hand, some of the sharks squad Galeiformes enjoy such a good reputation that divers and swimmers sometimes treat them with undue levity. Some scuba divers made, for example, to drag the tail of the shark-nurse (Ginglymostoma cirratum), which is considered harmless; and yet it is a dangerous delusion. Nurse shark has a flattened body and reaches up to 3.7 metres in length. It feeds on sea urchins, crabs, squids, spiny lobsters and small fish. In underwater caves and under overhanging underwater cliffs going to sometimes dozens of nurse sharks and other scuba divers swim among them with the nonchalance with which people walk amongst the sheep. However, the nurse shark is not always peaceful and friendly and not once were hurting people, disturbed their peace. Theodore Roosevelt III wrote in the March-April issue of the journal “Secrets of the sea” in 1973 about how it grabbed 30-inch nurse shark. His wife pulled the shark out of the water and threw it aside. Passing over Roosevelt in the air, the shark managed to grab his shoulder. Twenty minutes of “nurse” was hanging on his shoulder, in the end, I had to kill her and cut her jaw ligament.
1. This assumption is not warranted, and therefore it should be considered, at least, too bold. Penetration sharks in fresh water is likely a secondary phenomenon.