Piranha (also known as piranha) inhabits the main stream and larger tributaries, where the river is wide and the water is fast. Piranha is listed as the first of the four most dangerous aquatic creatures in the Amazon basin of Brazil. In Brazil, where piranha activities are the most frequent, about 1200 cattle are eaten by piranhas in the river every year. Some children playing in the water and women washing clothes are sometimes attacked by piranhas. Piranha is called "the wolf clan in the water" and "the water ghost" because of its fierce characteristics. Adult fish mainly feed at dawn and dusk, mainly insects, worms and fish, but some related species only eat fruits and seeds. The activities are mainly during the day, and will rest in a sheltered place at noon.

Mature piranhas have similar male and female appearance, bright green back, bright red abdomen and stripes on both sides of their bodies. Have a highly developed hearing. The jaw is short and powerful, the jaw is prominent, and the teeth are triangular and sharp, staggered up and down. After biting the prey, bite it tightly and tear off the meat with the twisting of the body. You can bite 16 cubic centimeter of meat in one bite. The rotation of teeth enables them to eat continuously, and a strong dentition can lead to serious bites.

During the breeding period, eggs will be laid at the roots of water, and the eggs are sticky. You can lay thousands of eggs at a time. The parent fish will protect the eggs, and the fertilized eggs will hatch after 9 ~ 10 days. The flooding of the river will affect the success rate of its reproduction.

Piranhas often appear in groups, each group will have a leader, others will follow the leader, and even the target. In the dry season, the water area becomes smaller, which makes piranhas gather in a large group, and animals or people passing through this water area are vulnerable to attack. For a long time, people think that the smell of blood is the main reason for the attack of large groups of piranhas, but some people think that the noise and splash from injured animals attract their attention.

As the saying goes, "Big fish eat small fish, small fish eat shrimp." However, in some lakes and rivers in the Amazon basin of South America, there is a kind of fish that is not afraid of big animals and is very aggressive.

So, what monsters lurk in these rivers and lakes?

American explorer Du Lin made a special trip to investigate. He witnessed a big bird trying to fish in the water. The big bird dived into the water, but struggled in the water and finally sank into the water. Du Lin was very surprised. To solve this mystery, he tied a goat with a rope and pushed it into the water. In less than a few seconds, the lake churned violently. Five minutes later, he pulled up the rope and saw that there was only one goat bone left, and the meat on the bone had been chewed clean.

Du Lin found several small fish with strange shapes in the sternum of goats. They jump around on the grass and bite anything they touch. Their heads are black on both sides, and their bellies are orange, only 6 cm to 7 cm long. Strangely, the little fish has two rows of teeth as sharp as swords in its mouth.

Through research, it is found that this is a unique "piranha" in the Amazon river basin, and the locals call it "water ghost".