BEIJING -- China's nearshore seawater pollution is still severe and its seawater quality degraded in 2012, according to data revealed on Wednesday by the country's State Oceanic Administration (SOA).

Last year saw around 68,000 square km of nearshore waters graded as the worst level of seawater quality, which is only suitable for sea ports and oceanic development. This was 24,000 square km more than 2011, the SOA said.

It added that a total of 170,000 square km of nearshore waters have not reached the first grade of seawater quality, which is suitable for marine fishery and marine natural reserves.

According to the administration, in 2012, about 19,000 square km of neashore waters were affected by eutrophication, a process in which water bodies receive excess nutrients that stimulate the excessive growth of plants such as algae and nuisance weeds.