tonight on a special edition of "nightline," a city underwater. dramatic rescues from the sky. bedridden patients carried out of nursing homes. but now even evacuation shelters are flooding. we're with one family returning to the place they used to call home. chainsawing through the wreckage. what they find. and tonight an alarming new threat. the owner of a chemical plant warning the place is poised to explode. plus, harvey's angels. incredible acts of heroism and sacrifice. businesses opening their doors to hundreds in need. >> lots of beds. lots of food. we've got water. and we can even bring your animals. >> and a joyful reunion. the grandmother rescued by a stranger on a jet-ski and brought together with her savior, finally learning his identity.

>> i was just thanking the lord for you guys. and a glimmer of hope in one flood shelter. a group of gospel singers lifting spirits with a song. ♪ >> this special edition of "nightline," "city underwat underwater: catastrophe in houston," will be right back.

>> announcer: this is a special edition of "nightline," "city

underwater: catastrophe in houston." good evening. and we are dedicating our show once again tonight to the fast-moving and often horrifying developments out of texas. the rain has largely subsided in houston, but much of that city is underwater and in crisis. tonight you will see rescuers working under extraordinary conditions and survivors displaying unimaginable resilience. abc's rob marciano is right there. >> reporter: houstonians are still trying to get their heads above water. this city ravaged by harvey. as rescues continue for the fifth straight day. by boat -- >> we're coming right back. >> reporter: -- and from the air. above fort arthur, texas harvey did not let up. in a cbb air marine ops blackhawk -- >> witnessing it up close is surreal. they are true heroes. >> reporter: -- we first rescued an elderly couple and their dog, stranded in their neighborhood. this woman soaking wet.

>> patient's inside. >> reporter: hoisted up by basket. we've already made one dramatic rescue. now we're right back at it. next the man and his dog. all safe tonight. as if the people of texas haven't been through enough, now even the shelters are flooding. >> river inside, outside, upside, down side. >> reporter: at the bob bauer civic center in port arthur, residents were forced to move to the bleachers to avoid the pooling water. >> and enough is enough. >> we're now also dealing with catastrophic conditions in southeast texas. and those conditions are a threat to life and property. >> reporter: harvey now a tropical depression has dropped more than 20 trillion gallons of rain in texas and louisiana. at least 31 are now dead. more than 13,000 people rescued so far. officials going door to door marking bright red orange cs on homes that are clear. authorities estimating up to

40,000 homes in harris county alone are destroyed. >> but 100,000 is certainly not out of the question. >> reporter: at greens bayou receding water revealing a grim discovery. inside that van the bodies of six members of the saldivar family. 84-year-old patriarch manuel and his wife bellia and their four great grandchildren, the youngest just 6 years old. >> family, i just notified them. obviously, they are devastated as we all are as well. >> reporter: they were swept away sunday as they tried to escape the flood waters. sammy saldivar the sole survivor. yesterday his brother rick spoke with my colleague tom llamas. >> they went together. that's all i can -- you know, that's all i'm happy for, that they went together. that's the only thing you can. >> reporter: almost 100 miles away rescuers are trying to save over 73 elderly residents, many bedridden, stuck in their nursing home for 24 hours. the entire facility enveloped by

water. foti calerges at ktrk, abc's own station in houston k took us inside. >> there are many other patients here in beds and they have to have people lift up their beds and try to carry them out. >> do you work here? >> yeah, at night. >> at nighttime. what does it been here? this water just rised all the way -- >> you know what? i was staying at home watching television and i saw this on tv. i could not believe they were still here. so i waded through the water and somebody gave me a ride on a boat to be here. it just breaks my heart. >> reporter: residents were corralled in the front entranceway. the front driveway turned into a canal. a flotilla of boats lined up as rescuers lifted residents still in their beds one by one. >> one, two, three, up. >> reporter: carefully placing them aboard to be reunited with family members. >> but still -- >> reporter: some of the most critical later evacuated by helicopter. in crosby, texas a new danger

coming from a flooded manufacturing plant. the ceo of arkema, inc. saying in a statement today that given current conditions at the plant chemicals could explode or catch fire. "there is no way to prevent it." everyone living within a 1 1/2-mile radius has been ordered to evacuate. back in houston some brave residents who fled ravaged homes are starting to head back to see what's left. just days ago the community around spring, texas submerged. shazia ashref, a single mom with three kids, never expected the waters to get so high. today she was determined to face the reality of what remained. >> we're putting these socks on. the water's receded. so we really want to kind of take a look, go inside and, you know, do a little bit of an inventory, see what's salvageable if anything at all. >> reporter: but the journey to get home not easy. >> this is a street where my

kids play. they come off the bus at the end and they walk over here. thank you. >> reporter: and there isn't much to salvage among her belongings. >> oh. you can see like water marks all the way up to here. >> reporter: but she says she's determined to rebuild. on the other side of town residents already starting over. >> this is our home. >> reporter: this morning student volunteers were helping danielle krueger strip down the damaged floors and walls of her home. >> it's really surreal to see the damage. >> reporter: now a lifetime of memories just a pile of debris on the front yard. >> silly girl. >> reporter: the last five days have been an emotional roller coaster for many families. the weeks lost their home but gained a life. yesterday they welcomed a baby girl, laura lynn. [ baby crying ]

william weekes and his mother made the emotional journey home today to port aransas, texas. his wife unable to travel, recovering in the hospital. >> this is where my trailer started. that's it over there where the suv is. >> reporter: their mobile home picked up and tossed by the wind. toys and clothes scattered on the ground. >> look, i found bela's dress she wore to school. i bet if we wash it -- >> reporter: the dress emblazoned with an anchor, symbolic of this seaside community. >> so we're saving that for sure. >> reporter: for william it's all too much to bear. with the help of a neighbor he chainsaws through what was the roof of their mobile home. climbing, searching for, and finding precious items. >> this is the blanket that she was making for the baby. i'm trying to get it out.

>> yes, sir. we're strong. we're resilient. >> we are. thank you so much. >> that's what it's all about. >> it is. i'm just so grateful we're all okay. thank you all for everything. >> thank you. >> reporter: the strong people of texas picking up the pieces, putting life together again. for "nightline" i'm rob marciano in conrow, texas. next, the good samaritans opening their doors to flood victims and the emotional meeting this grandmother reuniting with the stranger on a jet-ski who saved her.

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since harvey roared ashore on friday night, we have seen the worst of mother nature and the best of human nature, with civilians joining the rescues and one businessman, the owner of a luxury furniture store, becoming a local hero. here's abc's matt gutman. >> reporter: if there's been a ray of sunshine poking through harvey's storm clouds, it's the flood of good samaritans flowing into houston. perhaps most notably that flotilla of private boat owners. >> this is unbelievable. >> reporter: risking their own safety to rescue hundreds of stranded homeowners. >> you know, we're a little different down here in the republic of texas.

we look after each other and we take care of our own. >> reporter: this now famous photo says it all. a man on a jet-ski rescuing houston grandmother karen spencer from her flooded home. another photo shows a second jet-skier retrieving her husband, j.c. both men left to do more rescues before the spencers could even catch their names. after the story went viral, the identities of the rescuers were revealed. the mother of one of the jess skooeers posting a message on facebook, "my son, an iraq and afghanistan veteran. thank you for your service and your continued service in houston, texas." >> hey, miss karen. >> it's good to see you. >> reporter: and just today "nightline" was able to connect the rescued couple with their previously anonymous saviors. their names? keith christiansen and winston savis jr. >> we thank you. >> no problem. i mean, someone has to do it. >> you're a hero.

you're a hero. >> i was just thanking the lord for you guys. and knowing that there are risks and now we've heard people killed. and trying to save other people. i'm so thankful. you know, so my heart was filled with gratitude. >> reporter: and all across houston we've seen plenty of others, including businesses answering the call. workers stuck inside this bakery during the storm decided to stay up all night baking bread to feed first responders. many residents also giving away free meals. and air bnb working with local hosts to provide free rooms for evacuees. >> okay. no problem. >> reporter: but you could argue no businessman has made a bigger splash than this textbook texan. jim mcinvale, better known as mattress mac. >> you want your furniture delivered when? >> save you money. >> reporter: owner of the high-end gallery furniture stores in houston. >> how can i help?

>> reporter: when harvey hit town, mac hit record on facebook, offering a free port in the store. >> we've got lots of beds, lots of foods, lots of water. you can even bring your animals. we welcome you if you need a place to stay. >> reporter: while the evacuees at the convention center are sleeping on cots or on the floor, here at mattress mac's they've got plush beds and soft leather couches. >> matt gutman. >> how are you doing? >> nice to meet you. how's this bed? >> oh, it's soft. >> i think it is the most fantastic thing that could have ever been done for us. for him to do this, it just goes above and beyond what i thought, you know, would happen. because i just thought we was going to go like to a shelter and, you know, it would be like really hard times for us right now. but now being here, oh, i'm so relaxed. >> at the end of the day we still want to sell this furniture. so we want to make people comfortable. we want them to feel safe.

we want to provide them with the needs, the essential needs that they have. >> reporter: okay. >> give them a place to take a shower and eat. and so we welcome them into our home like it's theirs. >> reporter: it's sunday gallery furniture says it's had hundreds of people staying at its stores. those folks have been getting room plus board. really good chow. tonight's menu, courtesy of a donation from a local restaurant. >> what are you eating there? >> prime rib with mashed potatoes. >> prime rib and mashed potatoes. bon appetit. the smiles here contagious. >> it's really, really good. >> reporter: this has also become a crash pad for a national guard company on break. these $12,000 beds quite the upgrade from their standard issue cots. and he's not concerned about any wear and tear. >> furniture's made to be set on, slept on, laid on, whatever.

it's a product. it ain't going to hurt it. >> are you going to resell the product afterwards? >> absolutely. we'll have a harvey floor model sale or something. i'll come up with some shtick. >> reporter: but beyond the comfy digs there's something you can't put a price tag on, and that is peace of mind. >> when it said gallery furniture, i was like they've got to be joking. >> reporter: for the last three days carol, her daughter and two grandsons have called this living room display home. displaced by harvey, carol is also a survivor of hurricane katrina in 2005. >> so you were also in katrina. >> i was also in katrina. i never thought i'd be in here that we would go experience the same thing. but we did. >> reporter: back then she was trapped on the sixth floor of a building in new orleans. >> we got rescued by the coast guard. and he took us to this convention center in new orleans. >> how many people were there? >> oh, hundreds and hundreds and hundreds. and it was horrible. >> reporter: this time she was rescued by the fire department, which brought her to mac's place. >> he didn't have to do this.

and he made it so comfortable. when i left home, i left home without some of my medications and some of my medical equipment. and they supplied it. >> reporter: meanwhile, celebrities have also stepped up to the plate. the kardashians have pledged half a million dollars to harvey relief. and sandra bullock has donated a million dollars. >> it's very tough to watch your city get hit by such a bad storm and not be there to help. >> reporter: and houston texans football star j.j. watt has launched a fund-raiser that's raked in over $7 million. >> it's an unbelievable thing to witness, what happens in a time of crisis. the most difficult times bring out the best in humanity. and i think that's what we're seeing right now. i think we're seeing humans helping humans. it doesn't matter. rich, poor, black, while. it doesn't matter. everybody's helping everybody. and i think that's what's most important at a time like this. >> reporter: from the big names to the unsung heroes, it's all a testament to the spirit of texas. >> and we are overcomers. >> yes, you are. >> and houston is destined to be a greater city than it has ever

been. and you wait. and you see. we're going to see some awesome things happen in houston. >> we will. >> waverunner. >> waverunner. >> reporter: for "nightline" i'm matt gutman in houston. >> our thanks to matt gutman. and we'll be right back. when you don't get enough sleep, and your body aches, you're not yourself. tylenol® pm relieves pain and helps you fall fast asleep and stay asleep. we give you a better night, you're a better you all day. and for your daytime pain relief, try tylenol® extra strength.

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tomorrow our parent company disney will hold a day of giving, a fund-raising effort that begins with gma in the morning then throughout the day on abc, freeform and radio disney as well as on all of our social media platforms. and to kick things off disney and our houston station ktrk have committed $1 million to the american red cross in support of hurricane relief. and you can donate right now. visit abc news.com. i want to thank you for watching abc news tonight. we're going to leave you with a glimmer of hope from one shelter in texas, where a group of gospel singers treated evacuees to an emotional performance. ♪

♪ see your kingdom ♪ we want to see ♪ we want to see your kingdom ♪ sweet jesus ♪ your glory ♪ saving us ♪ revival ♪ we want to see your kingdom ♪ we want to see your kingdom ♪ sing it again ♪ ♪ revival ♪

♪ ♪ ♪