Mayor David Camardelle closed the 8-mile-long island's beach to its 1,500 residents and the thousands more tourists who normally flock to the vacation spot to fish and swim, The Miami Herald reported Friday.
Lisa Rhobus, who runs the Cajun Holiday Motel, told the Herald all her rooms were booked before the disaster, but now every reservation has been canceled.
"The only paying people I have at Cajun Holiday are workers helping with the cleanup. This could just about kill Grand Isle," Rhobus said.
A giant oil slick 7 miles from Grand Isle was spotted from helicopters Friday.
"It's coming our way. All that oil you're seeing on Grand Isle beach now -- that's nothing compared to what's coming," one deputy sheriff told the Herald.