Two teenagers have died after getting into difficult in water as members of their family looked on, Norfolk Police said.
Emergency services were called to Thorpe Marshes Reserve in Trowse at around 4.50pm following reports two people were missing in the water.
Norfolk Police said the boy and girl were teenagers. It is believed the boy was aged 14 and the girl 16.
Chief Inspector Nathan Clark said: "Both bodies were discovered within water and were sadly pronounced dead at the scene."
Inquiries continue into the circumstances surrounding their deaths.
Mr Clark added that the force received calls from several members of the public as a crowd gathered by the waterside.
Relatives of the teenagers were at the scene and watched the struggle unfold.
"We were alerted to two people struggling in the water, there was a coordinated effort to locate them but unfortunately the two teenagers were found dead," Mr Clark said.
"We are very much keeping an open mind about what happened and are interviewing people at the scene, including family members.
"I would like to offer all my sympathies to them - I can't imagine anything more than tragic than losing two teenage kids."
Chief Fire Officer, Nigel Williams, from Norfolk Fire and Rescue said: "We responded quickly to the call, with up to 40 officers on the scene, including our dive team and urban search and rescue team.
"Tragically there was nothing we could do and two young people have lost their lives whilst in open water.
"My heartfelt condolences, and those from every firefighter at the scene, go out to the family at this terribly sad time."
Norfolk Fire and Rescue Service, East of England Ambulance Service, Search and Rescue, the Coastguard and the police helicopter all helped with the search.