Water police boats and divers returned to the river at first light on Monday morning, more than 36 hours after 34-year-old Matt Jarvis was reported missing.

Friends say they saw Mr Jarvis' arm in the water before he went under and never resurfaced.

Acting Inspector Teena Rolls said Mr Jarvis was drinking with a group at the barbecue area at the bottom of the Kangaroo Point cliffs when he walked off towards the water's edge about 7.45pm on Saturday.

"He was with a friend at the time who's turned her back and then she has heard a splash and heard a rustling of the trees and then she's called out and thinks it was Matt who was in the water," she said.

"The group's gone to the water and seen splashing and have entered the water in an attempt to locate the missing person but were unable to locate him at that time.

"Other witnesses state that they've observed an arm in the water before he went under and was not seen again."

Water police, volunteer marine rescue vessels, helicopters and police divers scoured the river at the weekend but found no trace of Mr Jarvis.

A helicopter would not be involved in the search on Monday, police said.

Inspector Rolls said police had been making inquiries at the weekend into whether Mr Jarvis got out of the river downstream.

"We will be searching for the rest of the day until we decide that either we locate him or then it's no longer viable to continue a search," she said.

"We're simultaneously doing the search of the river and we're also making some inquiries in Toowoomba and elsewhere [including] hospitals as well ... just to ensure that he hasn't actually surfaced somewhere."

Inspector Rolls said bike and foot patrols as far as Newstead and Indooroopilly were also done.

Mr Jarvis has been described as Caucasian, about 1.7 metres tall with a proportionate build, a fair complexion and long brown dreadlocks.

He was last seen wearing a long white sleeve shirt with black dots, dark green cargo pants, a white-coloured cap and Nike shoes.