The sheen already has stretched into shoreline habitat and remains unstopped and impossible to measure, raising fears that the ruptured well could be pouring more oil into the Gulf than estimated.
The Coast Guard has estimated that at least 1.6 million gallons of oil have spilled since the April 20 explosion that killed 11 workers.
The environmental mess could eclipse the Exxon Valdez disaster, when an oil tanker spilled 11 million gallons off Alaska's shores in 1989.
Because of the risk of oil contamination, Louisiana closed some fishing grounds and oyster beds.
Raymond Schmitt, a fisherman and guide in Venice, Louisiana, said the uncertainty around the 2010 disaster was frustrating as he has a family to support.
Schmitt, who put his life savings into buying his 24-foot Skeeter, was frustrated that the Louisiana government was stopping workers from taking their boats out and allowing BP to dictate the terms.
"There's no way in the world I would jeopardize anybody's life in any way. But what they are doing is they're letting an oil company tell a state what to do," he added.
The slick nearly tripled in just a day or so, growing from a spill the size of Rhode Island to something closer to the size of Puerto Rico, according to images collected from mostly European satellites and analyzed by the University of Miami.
Alabama's governor said his state was preparing for a worst-case scenario of 150,000 barrels, or more than six million gallons, per day.
At that rate the spill would amount to a Valdez-sized spill every two days - and the situation could last for months.
BP suggested in a 2009 exploration plan and environmental impact analysis for the well that an accident leading to a giant crude oil spill - and serious damage to beaches, fish and mammals - was unlikely, or virtually impossible.
A sheen of oil from the edges of the slick was washing up at Venice, Louisiana, and other extreme south eastern areas of Louisiana.
(Left: Mike Oswald of Plano, Texas, carries redfish that he caught ten miles south of the South Pass of the Mississippi River on the Louisiana coast in Venice, La., Friday. Oswald said that he did not spot oil during his excursion in the Gulf of Mexico.)
Several miles out, the normally blue-green Fulf waters were dotted with sticky, pea- to quarter-sized brown beads the consistency of tar.
High seas were forecast through Sunday and could push oil deep into the inlets, ponds, creeks and lakes that line the boot of south eastern Louisiana.
With the wind blowing from the south, the mess could reach the Mississippi, Alabama and Florida coasts by Monday.
Amid increased finger pointing, the government desperately cast about for new ideas for dealing with the growing environmental crisis.
President Obama halted any new offshore drilling projects unless rigs have new safeguards to prevent another disaster.