Hippopotamus is the third largest mammal on land after elephants and rhinos. It has a large and clumsy body, with a body length of 350-450 cm, a tail length of about 56 cm, and a weight of 3000-3500 kg, but it is relatively short and has extremely short limbs. The height at the shoulders is only 140-165 cm, not as high as half of the elephant. It has a thick head and a very large mouth, which is larger than that of any kind of animal on land, and can be opened at a 90-degree angle. The teeth in the mouth are also very large. Both incisors and canine teeth are fang-like, and are the main weapon of attack. The lower incisors do not grow upwards, but extend parallel to the front like a shovel. The length can reach 60-70 cm, and the weight is 2-3 kilograms, the length of canine teeth is about 75 cm. The eyes, nostrils, ear shells, etc. are all born on the upper end of the face, almost on the same plane. The skin is very thick, the thickness of the back and sides can reach 4-5 cm, it is dark brown and red purple, smooth and hairless, and only has some hair on the mouth, inner ears and tail. Each of the fore and hind limbs has 4 toes of almost equal size, with hoofs on the tips of the toes, which are shaped like flat claws with slightly webbed between the toes.
The hippo's body is covered by a thick layer of leather. The skin is blue-black with brick red markings. Except for some short hairs on the tail, there is almost no hair on the body. The hippo’s skin is extraordinarily thick, with a layer of fat inside, which allows it to float out of the water effortlessly. When a hippopotamus is exposed to the air, the amount of moisture on its skin evaporates much more than that of other mammals. There are no sweat glands on the skin of a hippopotamus, but there are other glands that can secrete a reddish moist substance similar to sunscreen. , And can prevent insect bites. Hippos cannot stay out of the water for too long. For this reason, hippos must stay in water or wet habitat to prevent dehydration.