(2) Rivers in Hainan Island flow into the ocean from the middle to the surrounding areas, showing the topographical characteristics of high in the middle and low in the surrounding areas;
(3) Over the years, the South China Sea of China has been invaded by some neighboring countries. The reason is that the South China Sea is rich in oil and gas, fisheries, minerals, salt industry, tropical marine tourism resources and other resources, which is the main artery of maritime traffic connecting the Pacific Ocean and the Indian Ocean and has an important strategic position;
(4) For the sustainable development of the ocean, its good advice is to legislate to protect the marine ecological environment and prevent marine pollution, such as not discharging untreated sewage and garbage into the ocean.
So the answer is:
(1) Haikou; Qiongzhou;
(2) Flowing into the ocean from the middle in all directions; High in the middle and low around;
(3) The South China Sea is rich in resources, such as oil and gas, fisheries, minerals, salt industry and tropical marine tourism resources. It is an important maritime traffic artery connecting the Pacific Ocean and the Indian Ocean, and its strategic position is important;
(4) Legislative management to protect the marine ecological environment and prevent marine pollution, such as not discharging untreated sewage and garbage into the ocean.