A two-year-old girl died in hospital after falling in the sea, police said.
The toddler was airlifted to a London hospital in a critical condition after being recovered from the water at the Warren Apron near Folkestone, Kent.
However despite efforts to save her, she died later, a spokeswoman for Kent Police said.
An eight-month-old boy who also fell in the sea was taken to the William Harvey Hospital in Ashford where he was said to be in a stable condition.
Dover Coastguard said it was contacted after reports that a child's pushchair had tumbled into the water.
A spokesman said the Dover RNLI lifeboat was launched but the two children were rescued by members of the public, who pulled the toddler out of the sea unconscious.
Two adults, a man and a woman, were also taken to hospital in Ashford as a precaution.
A spokeswoman for South East Coast Ambulance Service said: "They were cold and wet and obviously shaken up.
"The two children were in a more serious condition."
