The bodies of a man and woman were found in 7 feet of water at a home in Plaquemines Parish, Louisiana, which was hit hard by Isaac, officials said late Thursday.
An autopsy will be conducted to determine the cause of the death of the couple, described as in being their 40s, parish president Billy Nungesser told CNN. The two were found late Thursday afternoon in the dwelling's kitchen.
The house is on the parish's East Bank, said Commander Terry Rutherford of the Plaquemines Parish Sheriff's Office.
Officials in Mississippi earlier reported a storm-related death.
A tow truck driver attempting to clear debris on a road was struck and killed by a falling tree, officials said. The incident took place at midnight, said Amanda Harris, deputy director of the Pearl River County Emergency Management office. The National Weather Service said it received reports of the fatality in Picayune.
Weary residents in Louisiana and Mississippi, meanwhile, began moving into recovery mode Thursday as a weakened Isaac dumped additional rain during its slow trek northward.
Amid the flooding, there was good news: All coastal warnings were discontinued, utility workers were making progress and more roads were reopening.
Isaac, downgraded from a tropical storm to a tropical depression, was still causing problems, though.
CNN iReporter Gerard Braud had no water or power at his home in Mandeville, Louisiana, on the northern shores of Lake Pontchartrain.
"It comes to a point when the lake and your yard become one," he said of 36 hours of constant waves. Fortunately, water levels beneath his home, which is built on pilings, had dropped a few feet by Thursday night.
Braud continued to use a canoe to get around Thursday. "Some friends made gumbo for me. I paddled five blocks to dry land and they gave me dinner."
An earthen dam on 700-acre Lake Tangipahoa in Mississippi was holding its own and not leaking late Thursday, despite significant damage, according to the Pike County Emergency Management Agency.
Agency director Richard Coghlan said a "controlled breach" or spillway will be created at the Percy Quin State Park lake to relieve pressure and drain it.
Crews were working carefully overnight, moving in equipment to prepare for the operation expected to commence later Friday once water levels drop a bit. "They don't want to influence the level of the river any more than they have to."
Residents of 19 houses and seven mobile homes, along with three businesses, below the lake were asked to evacuate.
The Mississippi Emergency Management Agency does not expect a catastrophic event, said spokesman Greg Flynn. Coghlan agreed with that assessment.
Downstream in Louisiana, Tangipahoa Parish President Gordon Burgess called for a mandatory evacuation for those living within a half mile of the Tangipahoa River.
Louisiana Gov. Bobby Jindal said the move was a precaution because if the dam were to break it would only take 90 minutes for floodwaters to get to Kentwood, a town of about 2,200 residents.
Later Thursday, Burgess said he did not know how many people had been evacuated along the 54-mile stretch of the river. Kentwood saw 75 people move.
"I'm feeling much more comfortable tonight and I'm going to sleep better tonight," Burgess said.
The river at Kentwood was observed at 15 feet Thursday evening -- more than two feet above flood stage, the National Weather Service said, predicting that the river will reach 16 feet Friday before a gradual decline.
Xanvanica Brumfield was among the evacuees at a school gymnasium in Kentwood. She and her four children left their home as high waters rolled in.
"I am ready to get it over with," Brumfield told CNN affiliate WFAA. "It's hot. Nothing really to eat and the kids are wearing me. I am ready to get back home and get situated."
Officials, meanwhile, intentionally breached a levee in Plaquemines Parish, southeast of New Orleans. The move was needed to help drain floodwaters in the Braithwaite and Scarsdale communities.
The storm has had a "major impact" on Mississippi, Gov. Phil Bryant said in Gulfport. "This is a man-made beach," he said, indicating the area where he was standing. "Most of that sand is gone. Thousands of homes have been damaged; people have been out of their homes and will be."