The body of the first victim, named locally as Alicia Williams, 25, a mother of one, was found on a sandbank in the River Clywedog, near Wrexham, Wales, on Wednesday evening.
Police launched a search of the river after witnesses told them a young couple were seen walking “four or five” dogs a short time before.
More than 20 volunteers, including fire and mountain rescue crews, took part in the operation until the second body was found nearby yesterday.
The man is believed to be Ms Williams’s boyfriend, David Platt, 25, who worked at a farm building children’s playpens. Police said the couple’s dogs had been recovered safely.
Detective Chief Inspector Mark Pierce said: “The two deaths are unexplained, but the likely scenario is at the moment that there was unfortunately a tragic accident.
“We believe the couple were here with dogs and at the time the river was swollen. The river level was at a higher level than it is at the moment.”
He said the families of the victims were suffering a “huge amount of distress” as they prepared for formal identification.
A post-mortem examination will take place today to establish the cause of death.