An area the size of a football pitch has been swamped with the gunk in China's port city of Quingdao, Shandong province.
But it hasn't put off beach lovers, who have been doing their best to enjoy the slop.
Some have managed to swim through it, while others have taken to rubber rings to laze on top of it.
But there have been complaints over the stench of the algae, which is releasing foul smelling gases.And environmentalists have also been up in arms over the 300m blanket, which consumes large quantities of oxygen and is incapacitating marine life and fishing industries.
Over 240 tonnes of the gunge has already been removed by volunteers working for the government's clean-up campaign.
Now authorities fear the mess could spread across the Yellow Sea and engulf the east Chinese coast.
In 2007 a similar algae nightmare occurred and soldiers and residents were forced to shift tens of thousands of tons of the stuff to allow Olympic sailing events to take place