渤海
The Bohai Bay is one of the three bays that compose the Bohai Sea. The Bay is a semi-enclosed, fairly shallow water basin, with average depth below 10 m. It has relatively poor water exchange into the Bohai Sea, and in turn the Bohai Sea exchanges poorly with the Yellow Sea (it can take 40 to 200 years for complete water turnaround), which means that both silt and pollution runoff accumulates in the Bay.