1. Climate: Weihai, Qingdao and other northern seas are affected by monsoon, with cold and dry winters and warm and humid summers. In contrast, Sanya, Beihai and other South China Seas are located in the tropics, with short spring and autumn, long summer, no ice and snow in winter, mild seasons, humid air and abundant rainfall.

2. Water quality: The water quality in the northern sea area is relatively soft, and the water color is yellow due to the high sediment content. In contrast, the water quality in the South China Sea is more transparent and the color of water is bluer.

3. Biology: Affected by the confluence of cold and warm ocean currents, the northern waters are rich in nutrients and rich in seafood, such as sea cucumber and abalone in Weihai and Qingdao. However, due to the high water temperature in the southern sea area, which is suitable for coral growth, the biodiversity of the seabed is high.

4. Landscape: The northern coastline is relatively straight, and the beach area is vast, mainly muddy beaches, such as Qingdao and Weihai. On the other hand, the southern coast is more tortuous, with many bedrock beaches and reef beaches, and the scenery is more spectacular. For example, Sanya has a unique tropical winding coastline and the Silver Beach in the North Sea.

Generally speaking, there are significant differences in climate, water quality, biology and landscape between the North Sea and the South China Sea, and each sea area has its own unique charm and characteristics.