GBARAMATU, Nigeria – When the tide rose under the rickety wooden house-on-stilts of Onitsha Joseph, a fisherwoman who lives above the twisting rivers of the Niger Delta in southern Nigeria, it brought a slick of crude oil.

Before long, she saw dead fish floating on oil inches thick, and fishing — her livelihood — became impossible. The fumes were so strong at one point that Joseph fainted. She was rushed to the hospital on a speedboat.

At first, she had no idea where it was coming from. Then, out with some other fisherwomen one day in February, she said they spotted something bubbling up to the river's surface. Joseph steered her oil-blackened canoe closer.

Far below her snaked a pipe. American oil giant Chevron laid that pipe 46 years before, according to many neighbors of Joseph who were there at the time, and now, they said, it was leaking.

So began a battle between Chevron and hundreds of fisherwomen in the Niger Delta. Chevron denies that oil was spilling from its pipes. But the women insisted that this was just another instance of oil companies refusing to take responsibility, and they decided to take the fight to the oil company's doors.

"You want to kill us with your oil," Joseph said, growing emotional. "We'll come to you so you can kill us yourselves. In person."

Oil companies like Chevron, Shell and Eni have made billions in profits in the vast Niger Delta region in the past decades. But now some are pulling out — and they are leaving utter ruin in their wake, according to government monitors and environmental and human rights organizations. The delicate ecosystem of the Niger Delta, once teeming with plant and animal life, is today one of the most polluted places on the planet.

It is the women, who do most of the fishing in the creeks and marshes in this part of the Niger Delta, who are trying to call the oil companies to account.

When they found the ominous bubbling, the fisherwomen alerted local leaders, who informed Chevron's Nigerian subsidiary. At first, Chevron ignored them, the local leaders said, and oil continued to flow through the line.

The fisherwomen decided it was time to occupy Chevron.

Hundreds of women from 18 communities, including Joseph, arrived at three Chevron facilities March 26. They climbed up Chevron's ladders. They scaled Chevron's wire fences, dropping down on the other side. They shook palm fronds and banged plastic bottles, singing protest songs.

Then they settled in to wait.

They vowed to occupy the facilities until Chevron did a proper investigation into the spill's cause.

Years of living with oil pollution made them resolute. Nigerian government agencies have counted tens of thousands of oil spills from many sources in the Niger Delta in the past 15 years — though data on spills varies widely. Tens of millions of barrels were spilled since production started in the 1950s, a 2011 study said — quadruple the volume spilled in the 2010 Gulf of Mexico disaster.

For years, the women had felt cheated by Chevron, the dominant oil company in their immediate area. Their villages were poor. By contrast, the Chevron facilities they were occupying were like small cities. They even produced electricity, though they didn't share it.

The fisherwomen didn't want Chevron out. They could barely imagine life without Chevron. The women just wanted the company to stop the pipe from leaking, to investigate — which could lead to compensation — and some sacks of cassava or rice to tide them over until they could fish again.

At night at Chevron's flow stations, the fisherwomen slept on hard metal walkways, plagued by mosquitoes. Occasionally, they paddled home to change clothes. Their lives were on pause.

Their impact was plain, though. Chevron says it shut off the flow of oil to its pipes in the area. The leak stopped, the women said.

After about 10 days, local male leaders asked them to leave. They said officials at Chevron had promised an investigation as soon as the women got out.

Their hopes raised, they got back on their boats, and went home to wait. But nobody came.

Both Chevron and Chevron Nigeria Ltd., the firm's local subsidiary, refused an interview. But a spokesperson for Chevron said in a statement that no joint investigation visit had been done because of "disagreements" among tribes. Aerial surveillance it carried out showed that no spill had come from its facilities, it added.

Women from the protest drifted back to their nets in mid-April. Their catches were pitiful.

They began to talk about returning to protest.

Joseph looked at the oil in the creases of her hands. She looked at the bags she once filled with crayfish to send to her children. They'd been empty for months. Oil or no oil, she would have to go fishing.

"I'm hungry," she said. "I want to try."