Emergency services, including an air ambulance were called to Coate Water, Swindon at about 19:30 BST on Friday, after reports a girl had collapsed.
Wiltshire Police said the 17-year-old was pronounced dead at the scene. Officers do not believe the death to be suspicious.
A spokesman said: "Our thoughts remain with the girl's family and friends at this extremely difficult time."
A teenage girl has died after suffering a cardiac arrest in a Wiltshire park.