“My house just started to flood,” he said in a phone interview. “We weren’t ready at all. It was very horrific for me and my mom.”

He said that the water had come in at a rate of about five or six inches an hour throughout the night, and he took videos of the flooding.

“At 1 it was in the garage, but by 4 it was at our ankles in the house,” he said. “By 7 we were just begging for help. We stood outside, we finally found someone who helped us.”

Speaking from a shelter in the city, he said that he and his mother had been rescued by men in boats, and that he did not know where they would stay in the immediate future.

“Seeing that coming through the door and the back door and the garage door like that, you’re helpless, you feel helpless,” he added. “It was the worst feeling I’ve had in a long time.”

Amber Robinson, 27, whose friend Keith Pinault tweeted on her behalf, was rescued with her parents, ages 67 and 61, after water flooded their home on Memorial Boulevard in Port Arthur. Mr. Pinault deleted the call for help once the family was rescued.

Ms. Robinson said Wednesday that they had known that the storm was coming but did not expect the rain to be as fierce or unforgiving as it was. Her family had expected water to flood in from the garage, but instead it started coming up through the floor and was soon waist deep.

The family put a flatbed truck in the garage and opened the garage door so that they could be seen by rescue workers. They were on the truck from 3 a.m. until around 10 a.m., when they were taken to a temporary shelter in a bowling alley.

“We don’t know where we’re going to go for sure,” she said. “But we are definitely better now.”

Michelle Preble, 45, in Oregon City, Ore., was one of many people on Twitter trying to compile a list of the addresses being tweeted into something that could be useful to emergency medical workers and others responding to victims.

In a phone interview Wednesday, Ms. Preble, who grew up in Houston and has many friends and family there, said that she had taken a list of names, addresses and conditions and passed them along to the Cajun Navy volunteer force. She was able to contact the Navy’s dispatcher through the walkie-talkie style communication app Zello.

She said that while it initially had been difficult to track whether individual requests for help were being answered by the group, she began to get confirmations Wednesday afternoon that the people whose addresses she had sent had been picked up by the Navy, including a 99-year-old man whose granddaughter had tweeted on his behalf.