Thomas Courto set off from the town of Wynyard around midday on October 18 with friends Isaiah Dixon and Bree-Anna Thomas in a yellow and white 17-foot motorboat.

The bodies of Mr Dixon and Ms Thomas were found washed ashore at nearby Table Cape on Wednesday afternoon.

Multi-beam sonar technology was used on Monday to comb an underwater area of roughly 340 hectares about three to four kilometres offshore.

"Unfortunately there has been no sighting of Thomas or the missing vessel," Inspector Steve Jones told reporters.

He said it was not likely Mr Courto would be alive at this stage.

Insp Jones said air and sea search efforts would not occur on Tuesday, when a review into the week-long operation would be undertaken to determine if any spots had been missed.

Searching may then resume on Wednesday.

Insp Jones described the search, which has been hampered by rough swells and wind, as one of the most comprehensive in the northwest in recent times.

Mr Courto's family and friends continue to search coastline in the area and are still holding hope of finding him alive, Insp Jones said.

The trio, all from the northwest, were reported missing on Monday afternoon when they failed to return.

They sat on a beach and went for a swim under a waterfall on their last day together, Isaiah's uncle, John-Paul Dixon, said last week.

Insp Jones said Isaiah's shirt had been recovered.

Australian Associated Press