Rescue workers carried out a search of Cleethorpes beach on Saturday.
A 15-year-old girl has died after being pulled from the sea on Cleethorpes beach, police have confirmed.
Humberside Police said the girl and boy, also aged 15, were airlifted to hospital at around 19:30 BST on Saturday.
The boy received treatment but was later released, the force said.
Both boys had been reported missing at around 14:00 BST, prompting a search involving an HM Coastguard helicopter and an RNLI lifeboat.
They left flowers at the site of the tragedy on Saturday
Flowers and tributes to the girl have been left in the place.
Police said the girl would not be officially named, at the request of her family.
Detective Inspector Nathan Reuben said: “Our thoughts and deepest condolences are with the family at this incredibly difficult time. We ask that they be given the time and space to process this tragic news. The family is supported by officers especially trained”.
“We are working together with all relevant agencies, including Humberside Fire and Rescue and the coast guard, to fully understand the circumstances of the tragic accident.”
An HM Coast Guard spokesman said a lifeboat was launched at 16:00 and found the couple “somehow” in the sea.
They said it had been a very difficult day for everyone involved.
Earlier, police thanked the public for helping with the search.