While China's oceanic environment is generally healthy, pollution in offshore waters remains high, a senior official from the State Oceanic Administration said on Tuesday.

More than 15 percent of coastal water is heavily polluted and is categorized as below Level IV - the lowest water quality level according to national standards, said China's Oceanic Development Report (2015), issued by the SOA.

"Severely polluted offshore waters are mainly concentrated in large estuaries and bays," said Jia Yu, deputy director of the China Institute for Marine Affairs. "The East China Sea remains the most polluted, with 46 percent of sea area below Level IV. It is also notable that pollution in the South China Sea shows a significant increase from 2010 to 2013," it said.