In the weeks and months that followed, the Huntington Station mother said, she kept expecting to hear Harlie's voice, calling out to her.
On dry land, the 34-foot cabin cruiser looked huge. Treanor said she suddenly felt ill as she saw where her daughter and two other children -- David Aureliano, 12, and Victoria Gaines, 7 -- had died. The other 24 passengers on the boat survived.
Treanor, speaking publicly about the tragedy for the first time, said last week she remains haunted by reports that it took two hours before a diver pulled out the victims.
"She could have had a fighting chance," Treanor said of Harlie, "but she wasn't given it."
No blame in accident
Treanor, 43, wasn't on the boat that night and said she doesn't blame anyone who was.
Not her ex-husband, Kevin Treanor, the boat's owner. Not Sal Aureliano, David's uncle, who said he was steering the boat during the accident -- shortly after those aboard had watched a fireworks display. Both men cared for the children who died and were experienced boaters, she said.
The Nassau district attorney's office has ruled out criminal charges, and a police investigation found that the Kandi Won met basic safety requirements. A final report on the accident is due out in a couple of months.
Aureliano has said the vessel was struck about 10 p.m. last July Fourth by a large wake, likely caused by another boat, that he couldn't see in the dark.
Harlie was pronounced dead at 3:48 a.m. the next morning at Syosset Hospital, her mother at her side. The Treanors' other daughter, Madyson, 8, who was also on the boat, wasn't hurt.
The Coast Guard responded immediately to a distress call and was at the scene in minutes, Joy Treanor said. But because a certified diver wasn't available, an underwater rescue wasn't attempted, she said.
"They had no certified divers or rescue swimmers," Treanor said. "They didn't go on the boat. They didn't try to break a door. They didn't even get wet.
"So you watched as these kids took their last breaths," she said, addressing the Coast Guard, "and you did nothing to save them."
Coast Guard spokeswoman Petty Officer 2nd Class Jetta Disco declined to respond to the allegations, saying the accident is still being investigated.
Nationally, the Coast Guard has few units equipped with divers, Disco said. Speaking hypothetically, she said that if divers are needed, responding Coast Guard units coordinate with other emergency-response teams to bring them in.
In the meantime, allowing someone in the water who wasn't a trained first-responder "could do more harm than good," she said.
Harlie would be in sixth grade now.
She was always smiling and had red hair that she let her mother style regularly, usually in a side braid. She loved softball and would do anything for her friends.
Treanor, who recently returned to her wholesale sales job after a seven-month hiatus, has learned to manage her grief with counseling. She wants to be strong for her ex-husband, for Harlie's classmates, who peppered her with questions at the wake, and for Madyson, who still talks to her big sister in her sleep.
"Harlie, don't go!" Madyson shouted one night, her mother said.
Treanor said she will not file a lawsuit -- "You'd be asking me to put a price on my child's head, and I can't do that." -- and hasn't advocated for boating-safety legislation, as the Gaines family has, because she doesn't believe those on the Kandi Won did anything unlawful.
She has, however, planned a golf fundraiser in Northport on June 10, which would have been Harlie's 12th birthday. Proceeds will help kids attend camp.
"Because she loves camp, loves it," Treanor said, "and I couldn't think of a better way to honor her."
Treanor said she wants others to know Harlie didn't suffer in her last hours. A bruise on her head showed that she was possibly knocked unconscious before she drowned, Treanor said.
At the hospital, Harlie looked as if she were simply asleep, her hair in the same ponytail Joy Treanor had set it in before the girl left to board the boat.
"The only comfort I get is how peaceful she looked," the mother said.