Grayson immediately went in after him.

"My guess is he was trying to get it. He slipped in the water, deep, he slipped away in the water," Grayson’s oldest son, Dafino Devega, told reach the child but were still struggling to recover his mother.

"Hey 911, can you come to Ed Stone Park?" the caller said in audio obtained by FOX 35. "We have a mother that’s drowned, and we got the baby, but we can’t get the mama."

The boater maneuvered close enough to pull the 4-year-old aboard. The boy was unharmed, according to authorities.

Witness Jon Reaka said Grayson appeared to expend all her energy ensuring her son survived.

"She spent all her energy trying to get her kid up over the edge," Reaka told FOX 35.

Reaka jumped over a railing and onto the boat, where he helped pull Grayson from the river. She was unresponsive when she was brought aboard.

"I jumped over the rail, jumped onto the boat and pulled the lady up onto the boat and, you know, we started CPR — I started CPR and mouth-to-mouth immediately," Reaka said.

Emergency medical personnel took over lifesaving measures after arriving at the park. Grayson was rushed to a hospital, where efforts to revive her continued for several hours.

She died in the intensive care unit around 10 p.m. Saturday, the sheriff’s office said.

"I tried everything I could do to save her," Reaka told FOX 35. "You know, I feel horrible. I mean, it’s so sad what happened."

Grayson was a mother of six whose final act reflected the fiercely protective way she had lived, her family said.

"That’s the type of mom that she was; she was a hero," Devega said.

"My mom, she was a strong woman," he added. "She would do anything to keep her kids safe."

Volusia County Sheriff Mike Chitwood praised the witnesses and the boater who rushed to help Grayson and her son.

"Sheriff Chitwood and the entire Volusia Sheriff's Office send sincere thanks all who jumped in to help with the rescue, and deepest condolences to Ms. Grayson's family and friends for their loss of a mother who gave her life to save her son," the department said in a statement.

Chitwood said Grayson would be remembered as a hero, "not just because of her final heroic act, but because she was a mom who would do anything for her kids."