When the ancients named it, even the word "whale" itself had a radical "fish". If it was written together with fish names such as mackerel and mackerel, it would make it even more difficult for people to recognize the true face of Lushan Mountain. This is not only true for Chinese characters, there are also similarities abroad. For example, in German, whales are called giant fish (walfisch). Until the 16th and 17th centuries, some natural science books treated whales as fish and recorded them together with fish. In fact, although whales look like fish, they are not fish, but a type of mammal. This is similar to the situation where bats look like birds but are not birds, but are also a type of real mammals. Whales are different from fish in that they are viviparous, usually giving birth to one calf per litter, and the young are fed and grown up by the mother's milk; while fish are oviparous and can lay thousands of eggs at a time. Once the young fish hatch, You can live independently without breastfeeding. The body temperature of whales is constant, with an average of 35.5°C, and this body temperature is maintained whether in cold waters or tropical sea areas; fish are cold-blooded animals, and their body temperatures change with changes in environmental temperature. Whales breathe with their lungs and need to surface frequently to breathe. Fish use their gills to absorb oxygen dissolved in the water, allowing them to stay underwater. The similarity in appearance between whales and fish is caused by them living in the same living environment for a long time, which is a "convergence phenomenon." Although whales are mammals, they bathe in the sea throughout their lives and are completely adapted to life in the sea. Whether it is the waters near the Antarctic or the Arctic Ocean, whether it is the equatorial waters or coastal sea areas, they can be found in their activity areas. Although the ocean is vast and vast, they can both catch food and find companions. They are one of the best swimmers in the ocean. When the sea is calm, they can swim leisurely, and when the waves are rough, they can still take a leisurely stroll. They can jump out of the water to "look at" the rising red sun, and they can also swim thousands of meters under the water to explore the mysteries of the deep sea, sinking and floating, and appearing and disappearing freely.