Chinese troops have cleared half a million tonnes of algae that was blocking the Olympic sailing course at Qingdao in eastern China.
A special zone was set up using a boom and netting.
But thick bright green algae still pollutes the beaches in other areas.
The water at the Olympic sailing course in Qingdao is now largely algae free.
Some 10,000 troops from the People's Liberation Army lifted over half a million tonnes of the thick heavy weed from the coastline.
Olympic sailing teams say they can now train and will be able to compete in Qingdao's waters.