The beaches of Qingdao, in China, have been invaded by 20,000 tons of bright green algae.
Qingdao, one of the best surfing cities in China, has seen an historical algae bloom over an area of about 11,500 square miles.
The cleanup costs will rise up to $30 million. Researchers believe that the algae that washes up around Qingdao has traveled from seaweed farms along the coast of Jiangsu Province.
This "sea lettuce", as it is known in Chinese, is harmless to humans but may kill marine life by sucking oxygen from the water.
Qingdao is one of the 20 largest cities in China, with an estimate population of 8.7 million citizens. Its temperate weather attracts many tourists to the local beaches.