Desperate flood victims have turned to social media to plea for assistance from volunteer rescue groups that have stepped up to assist authorities.

As the likely record-smashing floods from Hurricane Harvey devastated the Houston region Sunday, victims trapped in the rising waters begged for help on Facebook and Twitter.

Volunteer groups like the Cajun Navy, a coalition of leisure boat owners that perform search and rescue, heeded the pleas as emergency services were stretched beyond capacity by the scale of the devastation.

Facebook pages for the Cajun Navy and others created for rescue information were flooded with requests for assistance throughout Sunday as the waters continued to rise.

Children sleep on a counter to avoid the rising water. One of them is said to be on a ventilator

Residents who escaped onto rooftops posted pictures with their pleas for assistance

A desperate friend said that these girls were stranded on a bridge as the waters rose

This family took a picture of the rising water outside their home as they begged for assistance

The Cajun Navy indicated that they had rescued this elderly bedridden woman

Many of those turning to volunteers for rescue were elderly, sick, or children

Water has risen to neck level in Richmond, southwest of Houston, according to this post

Rescuers in turn called upon anyone in the region with a boat to join the effort and announced rally points for search and rescue staging.

'We need all the hands and boats that can be brought. We have the full green light to enter,' wrote Cajun Navy organizer Jon Bridgers Sr.

The heartbreaking pleas for assistance included many on behalf of vulnerable children, elderly and medically vulnerable people.

'My friend and her family are stuck on top of their roof,' one woman wrote in a bid for help. 'There are 3 people and a dog. The mother has a knee injury and is recovering from surgery so she can not get up on the roof and is waiting in the attic.

'Can ANYONE help this elderly bedridden sweet lady on the north side?' a reporter for a local news station wrote. 'Water is rising around her hospital bed.'

Members of the Cajun Navy volunteers are seen performing search and rescue operations

Residents all over the Houston area turned to Facebook to plea for help as waters rose Sunday

This family of five needed rescue from the rising water after Harvey inundated the area

Rescuers reminded anyone seeking help to post a phone number to verify the need for rescue

'Can ANYONE help this elderly bedridden sweet lady on the north side? Water is rising around her hospital bed inside her home. Her daughter & grandson are desperate,' a reporter for a local TV news station posted.

'One of out elderly foster families is sitting in three feet of water in Bellaire,' a Houston suburb, another person wrote. 'They've been there since midnight!! They cannot get to the roof because of physical and medical limitations so rescuers keep missing them.'

'Family with kids and senior....water up to their necks. please copy and share,' read one request for assistance.

One family of five asked for help and posted photos showing that they had written vital information on their special needs son's arm. 'THEY HAVE A SERVICE DOG THAT MUST GO WITH THE AUTISTIC CHILD!!!!!' a family friend wrote.

The family of this special needs child has written his information on his arm in a plea for help

A woman and her children and mother were apparently trapped under a bridge in the flood

Since Thursday some parts of Houston have already received 25 inches of rain and some suburbs have gotten 27 inches.

The National Weather Service issued a forecast saying the city could get as much as 50 inches, which would be the highest amount ever recorded in Texas.

'The breadth and intensity of this rainfall is beyond anything experienced before,' the National Weather Service said in a statement.

Houston Mayor Sylvester Turner said in a press conference Sunday that authorities have received more than 2,000 calls for help with more coming in.

Rescuers had to give top priority to life-and-death situations, leaving many affected families to fend for themselves. And several hospitals in the Houston area were evacuated due to the rising waters.

Rescuers had good advice for horse owners who were forced to leave the animals behind

Terror as the water reached several feet deep and desperate please went out on Facebook

A desperate daughter begs for help for her mother from anyone with a boat

A post from 'Cajun Navy' volunteer Gary Davis on a Hurricane Harvey Facebook page called for addresses and phone numbers of people who need to be rescued in Dickinson, Texas.

'This is what we need from YOU ALL. We are here to search and rescue. We are a well oiled machine but we need your help also. What we are looking for is addresses and CONTACT numbers of people who need to be rescued.

'We have multiple boats enroute. We try to avoid going on blind missions so point of contacts and names are a must if you can. Please be patient with us we are here for you all. GOD BLESS TEXAS. We got your backs.'

Bridgers told WAFB that the images and messages coming from the affected areas of Texas bring back memories from flooding in Louisiana last summer.

'Don't give up hope. We're coming as quick as we can,' he said.