The accident happened just off West 96th Street in Riverside Park just after 10:00 a.m.
Another driver, who avoided a collision with the woman, watched as she drove through a park, collided with a guard rail and went into the water.
The black Toyota Camry came to a rest partially submerged in the waters off West 96th Street.
Police say the woman climbed out of the car and yelled that she made a mistake and needed help.
Two Emergency Services Unit officers arrived quickly and rescued the 42-year-old woman.
She was taken to the hospital for treatment, and authorities said she is undergoing a psychiatric evaluation after making comments about recent family problems.
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