WASHINGTON, N.C. — As the flat-bottomed fishing boat crept into a swirling river that had once been Summer Haven Lane, Tray Tillman scanned the brown floodwaters and half-submerged houses in search of somebody to save.

“Today it’s been women and kids,” Mr. Tillman said.

Mr. Tillman, 26, a construction foreman, was part of a makeshift rescue flotilla that has plucked hundreds of stranded people from attics, second-floor bedrooms, church vestibules and crumbling decks as relentless, record-setting rains from Tropical Storm Florence flood rivers across the Carolinas and send torrents of water through downtowns miles away from the coast.

Inland flooding is perhaps the biggest continuing danger as Florence trudges through the Carolinas, and an improvised network of volunteers, some helping from as far away as Africa, has sprung up to locate and rescue people who did not evacuate. Harnett County, N.C., which is in the path of a river that was expected to crest overnight at 17 feet above flood stage, was one of many jurisdictions that ordered new evacuations. At least six deaths were confirmed by Saturday afternoon.

“They’re used to flooding, but nothing like this,” said Dan DiRenzo, who steered the boats with New Jersey Task Force One Urban Search and Rescue, one of the teams deployed by the Federal Emergency Management Agency to North Carolina, South Carolina and Virginia.