Faint fingers of oily sheen have reached the mouth of Mississippi River, the vanguard of a massive spill in the Gulf of Mexico.
The slick is making its way toward a delicate environment of birds, marine life and some of the nation's richest seafood grounds.
By sunset Thursday, the oil had creeped into South Pass of the river and was lapping at the shoreline in long, thin lines.
Booms in place to protect grasslands and sandy beaches are being over topped by 5-foot waves of oily water in choppy seas.
In the distance, the lights of the fleet of boats working to keep more of the crude oil away from the coast were outlined in the dying twilight.