Volusia County Sheriff Ben Johnson said Ebony Wilkerson, 32, who is pregnant, also faces three counts of aggravated child abuse when she tried to drive her van into the surf at Daytona Beach earlier this week, NBC News reported.
As she drove into the surf, Wilkerson locked the vehicle's doors, rolled up the windows and told the children to close their eyes and go to sleep, investigators said.
"You're supposed to protect your children at all costs," Johnson said. "You're not supposed to be trying to kill your children."
Johnson said the investigation found Wilkerson tried to stop rescuers from helping the children and that her 9-year-old son tried to fight her for the steering wheel at one point, NBC News reported.
Wilkerson was moved from a hospital where she was undergoing a mental health evaluation to jail, the sheriff said.
The boy and two girls, ages 3 and 10, who were hospitalized but not seriously hurt, were in protective custody, NBC News said.
The 10-year-old told investigators that their mother took them to the beach "so we could die," the sheriff's department said.