Houston came to her daughter's rescue that night, but no one could help Bobbi Kristina in January, 2015, when drug intoxication left her unresponsive in the bath at the Roswell, Georgia home she shared with Nick Gordon.
She was taken to a nearby hospital and placed in a medically-induced coma. Brown fought for her life for over five months until she passed away in July (15).
In an exclusive new Daily Mail Online interview, Nick, who is fighting a $10 million (£6.8 million) wrongful death lawsuit filed against him by Bobbi Kristina's court-appointed conservator, has recalled the horror of the morning he found his girlfriend face down and drowning in their bathroom.
"I blame myself for not getting to Krissy quick enough that day," Gordon, 26, tells Daily Mail Online.
And he recalls his late lover almost drowned in a tub once before, after falling into a drunken sleep while bathing.
Ironically, that incident took place the night before her mother died in the very same way at a hotel in Beverly Hills in 2012.
"It was in the Beverly Hills Hilton and the water overflowed out into the hallway," he says. "Whitney found her, pulled her out and slept in her bed that night."
Nick, who recently taped an emotional sit down chat with TV self-help guru Dr. Phil MCGraw, only wishes his late girlfriend had found the help he has since received for addiction issues that were spiralling out of control.
"I can't blame myself for another addict's addiction but I feel like I failed her," he says. "She didn't make it. I wish she got help. I wish she got my spot (in rehab). I did not protect her the way that I was supposed to - even if it was from herself."
Gordon checked into rehab following an attempted intervention by Dr. Phil on his show last year (Mar15), when Nick stopped the TV chat and stormed out as cameras rolled.
In his conversation with the Daily Mail Online, Nick also recalled the events that led up to Bobbi Kristina's ill-fated bath at their home last year, revealing the couple argued the night before after she accused him of partying with other girls, but he and his girlfriend made up and went to bed.
The following morning, he went downstairs to play videogames as Bobbi Kristina "got up and was doing her own thing". Her lifeless body was found in the bathtub later that morning by a houseguest.
"He knocked on the door and didn't hear a call from Krissy," he recalls. "He knocked on the bathroom and still didn't hear a call from Krissy and that's when he found her in the bathtub. Then he calls my name.
"I ran to my room and then I saw my girl on the floor. It was so traumatising. I dropped to my knees and kept giving her chest compressions and blowing into her mouth. I thought she was going to come round but that never happened."
Gordon also disputes the account of another houseguest, Daniella Bradley, who recounted Bobbi Kristina's final hours before she was found in the bathtub.
Bradley, who was one of the young star's closest friends, claimed Gordon punched and kicked Brown during a fight and then dragged her upstairs by her hair.
"I don't know why she said that," he says. "She's said a lot of things that aren't true."
Gordon's candid new interview with Dr. Phil will air in the U.S. on Thursday and Friday (28-29Apr16).