Bull shark, great white shark and tiger shark are the three fiercest sharks in the world. Bull sharks swam in the sea about 400 million years ago. It has always given human beings all kinds of horrible impressions. Cattle sharks are among the most aggressive, fierce and frequently attacking human beings, like great white sharks and tiger sharks. They are burly and look like a bull, with a disproportionately large mouth and staggered teeth, and are specially used to tear the meat of large animals. Recently, incidents such as "crashing a yacht", "swimming being attacked" and "shark's mouth grabbing a broken arm" occurred abroad are their masterpieces. Bull shark is one of the fiercest sharks in the world. It is listed as the most aggressive shark, the fiercest shark and the most frequently attacking human beings together with great white shark and sand tiger shark. It is often regarded as the "wolf of the sea", "killer of human beings", "mysterious killer of the sea" and "shipwreck butcher". Foreign events such as "crashing a yacht", "swimming being attacked" and "shark's mouth grabbing its arm" are the masterpieces of bull sharks. It can easily tear sea lions to pieces. Great white sharks are huge. They have a light cartilage skeleton and can reach 7 meters in length. Great white sharks will be found in any sea area with suitable temperature on the earth, such as South Africa, southern Australia and the waters near California. They have a good appetite, and almost any food they can catch can be a good meal for them. Sand tiger shark, also known as cone-toothed shark, is of great ornamental value. The sand tiger shark's olive-green skin with dark brown spots is shiny, with a long back and an inclined nose. Its eyes are small and fierce, and its head is small with a black spot in the center of its pale eyes. From its forever open mouth, visitors can clearly see its teeth that are as prominent and sharp as nails. The sand tiger shark's teeth are not as sharp as the great white shark's triangular sharp teeth like a chef's knife. Its front teeth are slender and sharp for biting prey, while its rear teeth have a file-like surface, which is conducive to biting and crushing prey. The teeth at the front of their jaws each have as many as four back teeth. Little sand tiger sharks use their teeth quickly and fatally. Sand tiger sharks, which are usually gentle and slow-moving, are definitely not always so gentle. If attacked, sand tiger sharks will fight back at lightning speed. Sand tiger sharks are also famous for their fierceness and ruthlessness in the marine world. Among the sharks listed in "International Shark Attack Archives" that attack humans for no reason, sand tiger sharks are among the best, along with bull-eyed sharks, ferrets and great whites. They also have two characteristics that other sharks don't have: first, most sharks have to move constantly to increase the oxygen content in their gills because of the lack of gill covers similar to bellows of bony fish. But the sand tiger shark is an exception. It can often remain almost motionless without suffocation. They also have a unique ability that other sharks don't have. They can suck air from the sea surface and reach a state of neutral buoyancy. Secondly, the sand tiger shark is a rare example of cannibalism in the uterus. The dominant embryo in the two wombs of the female sand tiger shark has teeth when it develops into a small shark with a length of 10 cm in the oocyst, and it will eat its hands and feet before it hatches into a super-large shark with a length of 1 meter. Finally, the strongest little shark came to the earth. Compared with other sharks, sand tiger sharks have innate predation ability, which seems to benefit from their rich experience in the mother.