The seas off China have been hit by their largest ever growth of algae, ocean officials said, with vast waves of green growth washing onto the shores of the Yellow Sea. However, it didn't stop beachgoers from swimming and playing in the green tide in the eastern city of Qingdao. The algae is not toxic nor detrimental to water quality. The State Oceanic Administration said on its website that the algae, enteromorpha prolifera, started to appear a week ago and had spread across an area of 7,500 square miles (28,900 square kilometres). The previous largest bloom was in 2008 when it affected around 13,000 square kilometres, it said.