A 16-year-old boy has died after the car he was travelling in plunged into a dyke in Lincolnshire.
The silver Citroen Xsara Picasso went into the water at Midville Road, Stickney, near Boston at about 1950 BST on Thursday.
A two-year-old girl and three others escaped with minor injuries and shock.
A police officer swam to the vehicle and freed the teenager, who was trapped, but the boy later died at Boston's Pilgrim Hospital.
The driver of the car, a 39-year-old woman from Dunmow in Essex, her two-year-old daughter and two boys aged 15 and 14 also from Dunmow, were taken to the Pilgrim Hospital for treatment.
The dead teenager was also from Dunmow.
The toddler was to be transferred to the Queen's Medical Centre at Nottingham for further treatment, police said.
The car was winched out of the water and the fire service's swift water rescue team did a thorough search to ensure no other people were in the dyke.
Police have appealed for witnesses to come forward.
Insp Gordon Richard, from the Force Command and Control Centre, said: "It was a gallant effort by the officer to rescue this young boy and it is a tragedy that despite the efforts of all the emergency service responders he died later in hospital."