A 27-year-old woman and 5-month-old baby girl died, and 12 others needed rescuing, when their boat capsized in the waters off lower Manhattan near Liberty Island, police said Sunday.

The vessel, described by police sources as a 21-foot Yamaha  boat, overturned just before 10:30 p.m. Saturday, officials said.

A passing boat helped rescue 12 people from the water before police arrived. NYPD divers found the woman and infant in critical condition in the water, cops said. They were rushed to NYU Langone Hospital-Brooklyn but could not be saved.

The other 12 were hospitalized with minor injuries.

Police are still investigating what caused the boat to overturn.