Deep-water turtles generally don't need to bask in their backs, but some species like to bask in the sun. A major feature of deep-water turtles is that they lurk in the water most of the time. Although they have no ability to breathe underwater, they still have a strong ability to hold their breath, such as crocodile turtles and pig-nosed turtles. These turtles rarely go ashore at other times except when they breed, so they don't need to bask in the sun, but some deep-water turtles need to bask in the sun.

1. Raise the temperature: The first advantage of drying its back is to raise the temperature. As a temperature-changing animal, the activity of tortoise is often closely related to the temperature. If the temperature is relatively low, the tortoise is not very active. On the contrary, after the temperature rises, its metabolism will accelerate, and it will love activities more.

2. Eliminate bacteria: Because sunlight contains ultraviolet rays, it still has a good killing effect on some bacteria, especially for turtles soaked in water for a long time, it is easy to have various fungi on their backs, which can be completely eliminated by basking in the sun, thus preventing various diseases.

3. Promote calcium absorption: Sun exposure can also promote calcium absorption. Although sun exposure can not supplement calcium, it can promote the synthesis of vitamin D3, which is of great help to calcium absorption, bone growth and soft nail disease.