HOUSTON (Reuters) - Jeremy Sparkman, a healthcare worker, cut short his vacation in the Ozark Mountains. Chris Pustejovksy, a horse wrangler, collected money and supplies and led a convoy down from Fort Worth. Rick Ngo, a surgeon, paddled over from a nearby subdivision.

Volunteers with boats return after looking for victims stuck in Tropical Storm Harvey floodwaters in western Houston, Texas August 30, 2017. REUTERS/Rick Wilking

On Wednesday, they joined dozens of other volunteers who piloted bass boats, jet skis and aluminum dinghies through the caramel-colored floodwaters of west Houston to ferry hundreds of residents to safety, part of an impromptu flotilla that has played a prominent role in the recovery from the worst storm to hit Texas in more than 50 years.

“I usually just use this boat for drinking beer,” said Sparkman as he steered his flat-bottomed boat around submerged pickup trucks. “But we come together when we need to - that’s what Texans do.”

Volunteers from as far away as Canada have converged on southeast Texas over the past week to help pull residents out of danger, giving a crucial boost to professional rescuers who have been at times overwhelmed by a storm that paralyzed the United States’ fourth largest city and displaced more than 1 million people in Texas and Louisiana.

Hundreds of boat owners called to offer their services on Sunday after the Harris County Department of Homeland Security asked for volunteers, briefly inundating a hotline set up for the purpose, spokesman Francisco Sanchez said. By the end of the day they had more volunteers than they needed.

Authorities took down their phone numbers and locations and dispatched them over the next several days to residents who called for help, pairing them up with professional rescue workers where possible.

“That got us over a crucial 24 hours when we were short,” Sanchez said.

Harvey dumped a record 50 inches of rain over parts of Houston, putting much of the sprawling city under water but leaving telecommunications networks largely intact. That has enabled rescuers to use cell phones, smartphone apps like Zello and social media to figure out where to go - either at the direction of professional responders or on their own.

Bruce Margolis, a retired Harris County emergency-services commissioner, put out an appeal on his Facebook team on Monday for boat owners to join his rescue effort and posted his cell phone number so flood victims could request help.

By Wednesday, his so-called Caveman Rescue Team had grown to about 15 volunteers who were camping out on his property and conducting rescue missions in Houston, Beaumont and Port Arthur. He had also raised more than $4,000 through a GoFundMe page to cover fuel and other expenses.

Standing knee-deep in flood water in a west Houston neighborhood, Margolis fielded a steady stream of phone calls as he helped residents clamber out of boats and onto a bridge that formed a rare spit of dry land. At the end of the day he said he had received 225 text messages requesting help.

Slideshow ( 3 images )

Nearby, Dallas resident Allie Boyter kept her eye on her iPhone in a waterproof bag, directing rescuers to specific addresses where evacuees had said other residents were still at risk. “I’m about to get on a jet ski and go save a cat for an 85-year-old lady,” she said.

DANGER LURKS IN NECK-DEEP WATER

Stranded residents have also turned to social media for help, posting their requests under the Twitter hashtag #harveysos. As of Thursday evening more than 4,000 of those residents had been rescued, according to Harvey SOS Tracker, a Web site set up to map those requests.

Local officials initially discouraged residents from posting their rescue appeals on Twitter and urged them to call 911 again. But emergency phone lines were jammed by Saturday afternoon and local officials tried to monitor Twitter and Facebook as well to pinpoint those in need.

The work can be risky. Two volunteers died and two more were missing after their boat was swept into a swollen river in northeast Houston on Monday, according to the Houston Chronicle. Another three people on the boat, including two journalists, were hospitalized.

Pustejovksy, the horse wrangler, said he had been bitten by fire ants and dodged alligators and snakes as he plunged through neck-deep water to carry people out of their homes.

“I told my boy if you don’t want to see stuff you ain’t never going to forget, don’t come,” he said. His 24-year-old son volunteered anyway, he said.

Despite the dangers, a sense of good cheer prevailed on Wednesday in a west Houston neighborhood that flooded when authorities released water from two nearby reservoirs that were in danger of spilling over.

“I used back muscles I didn’t know I had before,” said Ngo, who said he and a friend had paddled about 20 residents to safety in an inflatable raft. The surgeon said he heard about the need for help through his neighborhood men’s group.

Chris Manuel waded ashore with his five-year-old son, his wife and their miniature poodle - their second water rescue in after they abandoned their house and their friends’ house. “We’re taking it day by day. I’m a bit knackered,” he said.

As flood waters in Houston have receded and Harvey has wheeled east, officials say the demand for water rescues has abated. That has at times led to tensions between the professional rescuers and the citizen volunteers who lack their level of training.

With the wind picking up on Wednesday afternoon, FEMA officials ordered volunteers to pull back from the flooded neighborhood in west Houston.

Texas state trooper Brian Coleman, soaking wet after falling into a manhole, tried to break the news gently. “You’re doing a hell of a job,” he told one rescuer.

But when another volunteer began shouting about “disorganization,” Coleman put his foot down.

“Where’s your car? Walk that way now. See you later, sir,” he said to Jason Kugler, who marched back across the bridge.

“This is not my first hurricane!” Kugler shouted in response.

As the Texas National Guard and other professional rescue teams moved in, civilian volunteers traded tips about where to head next.

Others opted to keep up the search.

“You want to defy the law? I’m good with that,” Eric Soluri, a retired San Antonio policeman, told a friend as he quietly slipped his boat back into the floodwaters.