Coast Guard Admiral Thad Allen, the U.S. government's commander for operations in the Gulf, said cleanup crews would continue to attack the oil slick using surface dispersants, skimming and controlled burns.
Further inland, BP contractors assisted by flotillas of hired shrimp boats continued to string containment booms around sensitive coastal areas. And National Guard teams with bulldozers and helicopters pressed on to plug gaps in booms protecting Louisiana's storm-battered shoreline to prevent oil from reaching the fragile marshlands behind them.
Time may be running out on the marshes. Local TV footage late on Friday from a helicopter flight over Louisiana's barrier islands showed miles of oil slick carried by churning waves being washed through wide passes between the islands directly toward the wetlands of Terrebonne Parish.
Scientists and shrimpers alike have said repeatedly that contamination of the marshes, the foundation for the region's economy and way of life, would be devastating.
The vast but dwindling marshes are the nurseries for shrimp, oysters, crabs and fish that make Louisiana the leading producer of commercial seafood in the continental United States and a top destination for recreational anglers.
"I want to throw up right now," said Michael Gros, 51, a shrimp boat owner and captain from Larose, a town in the La Fourche Parish of Louisiana.
"I've been doing this for 22 years full time, and I don't really know nothing else," he said in a soft Cajun drawl. "If it doesn't come into our marsh and ruin our marsh, I'll be very surprised. Once the grass dies, it's gone."