Emergency crews scrambled to rescue three people in difficulty in the water at Marloes Sands beach in Pembrokeshire on 30 August.
Dyfed-Powys Police said two of those in trouble were able to return themselves to the shore.
Teams from the force, HM Coastguard and the RNLI launched a search for the missing teenager who was visiting the area on holiday from Yorkshire.
In a statement on Wednesday, Dyfed-Powys Police said: “Sadly, we can confirm that a body has been found during the search for a 15-year-old boy who was reported to have gotten into difficulty at Marloes Sands, Milford Haven on Sunday 30 August.
“Next of kin have been informed, and our thoughts are with them at this time.”
