Rescue crews and ordinary Texans worked to pull hundreds of Houston area residents from their homes and cars after Hurricane Harvey battered the city. (Taylor Turner/The Washington Post)

As Harvey moves across Texas, thousands of people have been stranded in flooded homes as roads transform into neck-high rivers.

At least 2,000 people have been rescued, according to the latest reports, but officials estimate that more than 30,000 people could be displaced. Some have turned to social media for help, posting desperate pleas as the rising waters have overwhelmed neighborhoods.

In Houston, the fire department has responded to more than 4,000 water-related calls for service. So officials turned to the public for help.

“We need citizens to be involved,” Federal Emergency Management Agency Administrator Brock Long said Monday. “We need the whole community. Not only the federal government forces, but this is a whole community effort from all levels of government and it’s going to require the citizens getting involved.”

Austin Seth, a senior at Texas A&M University at Galveston, joined the rescue efforts after he saw the Dickinson, Tex., police department ask for help from boat owners on Facebook.

To people in the Dickinson area: if you have a boat and would be willing to help the police department rescue people from their flooded homes, please call 281-337-4700.

Posted by Dickinson Police Department – Texas on Sunday, August 27, 2017

“It’s been unreal,” Seth told CNN. “I’ve been passed by dozens upon dozens of boats.”

Those other boat owners include people such as Howard Harris, who bought a boat the last time his home town of Cypress, Tex., flooded. Now he’s using the boat to help his neighbors.

“If anybody needs anything, I help the best I can,” Harris said. “I want everybody to be safe and to be able to get out of the neighborhood.”

Videos of people rescuing stranded residents spread across social media. In one clip that’s been retweeted more than 10,000 times, a man unloads his boat into the water after traveling from Texas City to Houston.

The reporter asks the man what his plan is, and the response is straight to the point: “I’m going to try to save some lives.”