The Garda Water Unit has joined the search for missing Kerry farmer Michael 'Mike' Gaine.
However, the unit found nothing after completing its search of a disused quarry about 3.2km from Mr Gaine's farmyard.
The garda divers are now focusing on a mountain lake in the area.
An extensive search has been ongoing since the 56-year-old was reported missing near Kenmare last Friday.
His farmyard remains sealed off as investigating gardaí continue with their search.
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Yesterday, the last of the slurry tanks were emptied and diggers continued to excavate outside the farm buildings, moving large amounts of earth.
An overgrown mountain stream and a ravine near the farm buildings were also searched extensively and an area near the stream was excavated.
Garda sources say they have yet to make a significant breakthrough, but that efforts are continuing.
Locals describe the disappearance of Mr Gaine as "a complete mystery".
Over the weekend a massive search operation took place.
The multi-agency effort included An Garda Síochána, Civil Defence, the Coastguard, Kerry Mountain Rescue and up to 200 volunteers.
The garda helicopter and drones have been involved in aerial surveys, while specially trained sniffer dogs have also been deployed in the search.
A vehicle was removed from the farmyard by gardaí on Saturday.
The initial search area was vast, comprising hundreds of acres of rough mountainous terrain on the southern slopes of the Dunkerron mountains, not far from popular tourist spot Moll's Gap.
Yesterday, however, gardaí did not request volunteer assistance, and the wider land search appeared to have been scaled back considerably.
While this is still being treated as a missing person case, gardaí say they are keeping an open mind.
Mr Gaine has been missing since last Thursday.
He was last seen in a shop in Kenmare town shortly before 10am when he purchased phone credit.
In renewing their appeal for information, gardaí issued a CCTV image of Mike Gaine captured in the shop where he was last seen.
Gardaí are also specifically asking anyone who may have dashcam footage taken last Thursday to Friday on the N71, the main road between Kenmare and Killarney or in the Moll's Gap area, to make that footage available.
