It is a mud hole that allows turtles to enter. As shown in the picture:

It likes cleanliness and is afraid of dirt, likes sunshine and is afraid of wind, and likes silence and is afraid of shock. In the natural environment, soft-shell turtles like to inhabit clean rivers, lakes, reservoirs, ponds and other waters. During the calm days, they often lie on the sunny shore and bask in the sun (commonly known as basking on their backs), using the ultraviolet rays in the sun to kill the harmful substances on the body surface. Pathogenic bacteria, promote the healing of injured body surfaces, increase body temperature through basking on the back, and promote food digestion. Turtles are very timid and are very sensitive to sounds and movement of objects in the surrounding environment. They will dive into the water at the slightest sign of disturbance. Turtles are ferocious and aggressive by nature, and bullying among groups is common. When food is scarce, they will cannibalize their own species. During its growth period, it mainly breathes through its lungs. When the water temperature falls below 15°C, the turtle dives into the mud at the bottom of the pond and begins hibernation, relying on auxiliary respiratory organs such as gill-like tissues in its throat to breathe.

Soft-shell turtle (Amyda Sincnsis) is the common name of soft-shelled turtle, also known as turtle and water fish. It is an oviparous amphibian and reptile. It is the general name for soft-shell aquatic turtles of the order Turtles and the family Turtles. ***There are more than 20 kinds. There are mainly Chinese soft-shelled turtles, Chinese mountain soft-shelled turtles, spotted soft-shelled turtles, and turtles existing in China, among which the Chinese soft-shelled turtle is the most common.

Turtle turtle is not only a delicacy on the dining table and a high-quality material for fine banquets, but also can be used as an ingredient in traditional Chinese medicine. It has many nourishing and medicinal effects, including clearing heat and nourishing yin, calming the liver and calming wind, softening and dispersing stagnation, and has effects on liver cirrhosis, hepatosplenomegaly, and epilepsy in children.