The grieving parents of a 16-year-old who disappeared in the waters off Jacob Riis Park spent Saturday keeping vigil at the beach as scuba divers scoured the sea for a second straight day to find the boy.

Elyjha Chandler and another teen have been missing since Friday night, when they stood in knee-high water — and were suddenly swept under, Chandler’s dad told The Post.

“He wasn’t far out in the water… One of the boys told me when the water hit them, it was like a demon coming at them,” said a stunned Urshell Chandler, who said Elyjha couldn’t swim, and came to the beach on a whim at the last minute instead of going to basketball practice.

Elyjha’s mother sat near the water’s edge in tears, in a folding chair, her legs shaking as she begged aloud for her son’s safe return.

“Why? Why? Why?” Aminatu Noah cried.

“I just want to stay here,” she said.

“I just want them to come back. I want them to walk up to us.”

“My only son,” she repeated while looking up at the sky.

“My God, let them come back. … God is control. I’m going to keep praying.”

Chandler and his 17-year-old friend, identified only as Christian, went in for a dip around 6:35 p.m. and never came out, a police spokeswoman said.

Lifeguards are stationed at the state park from 10 a.m. to 6 p.m. in the summer, according to the state’s website.

The family contended the lifeguards left early.

The state didn’t return a message seeking comment.

Elyjha and Christian were among four teens who went into the water, when a good Samaritan tried to get them out, Urshell Chandler said he was told.

“A man pulled him out. He was looking at Elijah. His eyes were opened wide. Elijah went up and down three times and then they didn’t see him again.”

“I was hoping he’ll come out of the water and say, ‘I’m here,’” the dad said, throwing his hands up in the air.

“It’s very hard. I cried. I could not sleep last night.”

His older sister Shawanda said Elyjha had enough credits to graduate this summer and head to college, but chose to stay with his friends.

“He’s the perfect little brother,” she said, describing him as sweet and “always smiling.”

Shawanda Chandler then burst into tears, recalling how Elyjha “was scared of the water.

“…It feels unfair to be alive. My brother was gonna do so much stuff.” 

The proud papa recalled his son’s love of basketball and school.

“His score was one of the highest in his class,” he said.

“He got so much awards for academic achievements — all the time.”

The dad was also still hoping beyond hope that his son was alive.

“I was out at the edge of the water looking,” the grief-stricken father said, “hoping to get a glimpse of my son.”

The Coast Guard announced late Saturday that they had called off the search for the boys.

“The decision to suspend a search is always difficult and weighs heavily on all involved,” said Capt. Jonathan Andrechik, commander of Coast Guard Sector New York in a press release. “Our crews, along with our partner agencies, have conducted an exhaustive search, and our thoughts remain with the families during this difficult time.” 

The Coast Guard said crews searched more than 600 square miles from Sandy Hook, New Jersey, to Long Beach, New York.