Police find body of 20-year-old man who went missing in the Fitzroy River

Police also rescued a trio who became stranded on the Ord River. (ABC Kimberley: Erin Parke)

Police in Western Australia's far north confirm they have found the body of a man last seen swimming in the flood-ravaged Fitzroy River on Sunday.

Fitzroy Crossing police started searching for the 20-year-old after the alarm was raised at 4:14pm yesterday but were unable to find him.

The man's family has been advised of the news and a report will be prepared for the coroner.

Boaters found safe

Meanwhile in Kununurra, a man in his 40s, woman in her 20s and a 15-year-old girl were found after being reported missing last night.

Friends of the group raised the alarm after they failed to return from their trip up the Ord River, having launched from Celebrity Tree Park in Kununurra on Sunday morning.

But police said the Kununurra residents were found safe floating downstream near Herbie's Hideaway, a waterfall on the Upper Ord, having run out of fuel.

"We had a chopper up near Herbie's, which managed to land nearby," Kununurra police officer Neil Vanderplank said.

"One of my officers has got across and had a yarn with the skipper, and had a quick check of their welfare.

The missing Kununurra group sheltered near Herbie's Hideaway after running out of fuel. (Supplied: Janice McDiarmid)

"They're all in good spirits — obviously a bit damp."

Senior Sergeant Vanderplank said the group had done the right thing by advising others of their likely departure and return times.

Department of Fire and Emergency Services boats have been dispatched up the Ord to tow the group back to Kununurra today.

Senior Sergeant Vanderplank said heavy rains had created challenging conditions on the river.

"The amount of water that's flowing in there at the moment, there are islands of floating weed and plant material floating along the river at a rate of knots," Senior Sergeant Vanderplank said.

"Pushing against that is going to chew your juice a lot faster, you really need to prepare and be aware of your surroundings."

Missing hikers rescued

Meanwhile, a pair of hikers missing in Mirima National Park on the outskirts of Kununurra were rescued this morning.

The pair were stranded by floodwater, and made contact with police about 6:40pm yesterday.

Recent rains have left rivers and creeks running high across the Kimberley, including in the Mirima National Park. (ABC Kimberley: Ted O'Connor)

Kununurra police attempted a rescue, but were forced back by floodwater, with the hikers forced to remain in place overnight.

They were rescued this morning by a helicopter and were likely to be treated by paramedics once they had returned to Kununurra.