Transcript for Volunteers rescue Hurricane Harvey victims, evacuation centers fill up
The red cross estimates that over 17,000 people in and around Houston will attempt to fall asleep tonight in a makeshift bed, wondering about their homes and even the safety of family members. The monumental flooding and humanitarian disaster continues to unfold after Harvey, with some areas receiving over 51 inches of rain, a record in the continental U.S. Official rescue teams are overwhelmed, and now more civilian groups pitching in. ABC's rob Marciano joined a team of volunteer military veterans in saving stranded survivors. Reporter: For the fourth straight day the storm that just won't go away dumped yet more water on a state still reeling. Nearly 7,000 people have been rescued. There they are. There they are. We're coming to get you. Oh, my goodness. Reporter: First responders and volunteers alike racing against rising flood waters. Look at that. I know. My goodness. Reporter: Trying to reach thousands of trapped families in Houston and the surrounding areas. Coast guard baskets hoisting so many of those trapped to safety. Helmet cameras showing the white-knuckle ride to their choppers above. In this suburb south of Houston a team of volunteers from galveston used their boats to navigate rivers that were once streets. They scour this area for hours, saving family after family. What's up, buddy? You all right? Reporter: My colleague Eva pilgrim was there with them. Okay. We're going to go. Where are they at? Are you okay? Reporter: Responding to cries for help from stranded families. When did the water start creeping up over here? Sunday. Sunday. Sunday morning we woke up and it was like that and it never went down. Reporter: Among this team is Michael Gibson, a firefighter who came back to his old neighborhood to help. He's been rescuing people here for four days. Today Gibson is more than just first responder. He's a worried son. My parents told me they were in the water. Reporter: Weaving through a graveyard of cars, he finally reaches their home. He's coming. Reporter: And gets them to safety. To the west in another Houston suburb we find a team of military veterans now volunteering to serve their country in a new way, traversing flood waters to help families. This is where we're comfortable. We're really good at being miserable. We're really good at being dirty. Here you know, we're not getting bullets whizzed by our ears. Reporter: Beau burns is here with team rubicon. You guys good? Reporter: A non-profit that responds to disasters around the world. When you go into a zone like this, you've got multiple teams, you do a rescue operation. What are the risks involved here? Lack of information I'm worried about. Lack of communication I'm worried about because water's getting ready to rise and these people don't want to leave their homes. Big family, little family. Reporter: In one home surrounded by rising waters we find a family of seven. They're emotional. But one by one the team brings them out. They have no idea what they're going through, but I can imagine. Reporter: And brings them to safety. We're coming right back. Yeah. We're coming right back. And you can come back with us if you want to help us. Lend a hand. We could use you. Reporter: The emotion there is just palpable. This family's having a hard time with this one. I'm glad team rubicon's here to help them out. Powerful stuff. These rescues are critical. Hurricane Harvey has already claimed lives. One of its victims police sergeant Steve Perez, who went missing trying to drive into work. We couldn't find him. And once our dive team got there, it was too treacherous to go under and look for him. Reporter: And the death toll is expected to rise as many people are still missing. Six of Rick Saldivar's families, four children, the youngest just 6 years old, and their great-grandparents, were trapped in their van and swept away by flood waters. Rick's brother is believed to be the only survivor. Rick spoke to my colleague Tom llamas. It's been a nightmare just waiting. How's your brother doing? He's blaming himself of course. He's blaming himself. Every time we go to hang up he says I'm so sorry. It's not your fault. You didn't know. Reporter: Rescuers using every measure possible to reach the displaced. This grandmother being rescued out of her flooded home on jet-ski. On rain-soaked streets a caravan of school buses escorted by police. This family had to evacuate their home and a neighbor's. We called and we got rescued probably around 11:00. Who took you guys here? A school bus. Reporter: They were brought to Lakewood church. The 52,000-member megachurch founded by pastor Joel Osteen, who after criticism yesterday as to whether the church would take displaced residents tweeted this morning, "Lakewood's doors are open and we are receiving anyone who needs shelter." This is the first day that we've really been able to because up until about 2:00 yesterday or maybe a little before that there was nine feet of water around this building. So you couldn't really get to this building at all. And this is the first day that we felt that we could -- we could actually facilitate a collection point. Reporter: Clothes and toiletries piling in from volunteers. Air mattresses line the floor of their gymnasium. This will be the first area we'll stage in, and then we'll move on to areas, other areas as well. Reporter: Across the city at the Houston convention center some evacuees are brought in by dump trucks. Almost all of them have lost everything. Our entire neighborhood was flooded. It looked like a lake. Like we were living on a lake. Reporter: 5,000 cots line the conference floor but there are 9,000 people here. City officials say they have things under control. We've had a very quiet night. With 9,000 people you're going to have a couple minor incidents. But they have all been minor this evening. People are sleeping well. Even the people who are out on cardboard and blankets. Reporter: There's a heavy police presence to protect the precious lives inside. Children, covered in blankets, their families trying to get some milk and some rest. After the nightmare they've lived through. My one objective is to take care of the women and the children. And yesterday we didn't have any of this. So to see how far we've come in 24 hours has been amazing. Lots of babies? Lots of babies, yes. We had a two-week-old. We had morltthers in labor yesterday. Reporter: For "Nightline" I'm rob Marciano in Kirkwood, Texas. And you can tune in to "Gma" tomorrow for an interview with Joel Osteen. The pastor of that Houston megachurch. But we turn now to ABC's Matt
This transcript has been automatically generated and may not be 100% accurate.