Story highlights In flooded Texas, civilians are opening their doors to victims and pulling them to safety

With emergency responders overwhelmed, these good Samaritans provide invaluable help

(CNN) In the thick of disaster, help doesn't always come from a helicopter or a rescuer in a uniform. Sometimes, it's a makeshift fleet of pickup trucks and johnboats, speeding toward danger as almost everyone else is trying to get out.

The Cajun Navy, the famous volunteer rescue group that formed in Louisiana after Hurricane Katrina, is mobilizing to Houston to deliver desperate residents from Harvey's downpour. Clyde Cain, who runs the group's social media, told CNN they started deploying people in the early hours of Monday morning.

"There are hundreds of volunteers and we've already made hundreds of rescues," he told CNN. "Our goal is to help people get out if they are trapped in their homes or apartments, get them to safety."

As Katrina survivors and witnesses, these men and women know what it's like to feel floodwaters rise around them with no guarantee of salvation.

In Houston, they now join locals and other out-of-towners who are patrolling waterlogged streets, opening their doors to strangers in need, offering their time and talents and choosing to help others instead of seeking higher ground.