The Garda Water Unit is now helping in the search for missing Kildare man Trevor Deely.
Officers have been searching an area in West Dublin after receiving a tip-off that his remains could be buried there.
Just over three weeks ago, gardaí began searching a woodland site in Capelizod for what they described as evidence in connection with the disappearance of Trevor Deely.
So far, only a gun has been recovered but officers have not said whether they believe it is connected or not.
The search site is located along the River Liffey and this afternoon members of the garda water unit have been drafted in to help.
Gardaí say they will continue to call on specialised units as they are required.
22-year-old Trevor Deely from Naas in Co Kildare disappeared almost 17 years ago while walking home from his Christmas Party near Baggot Street in Dublin.
Gardaí have described this search in Chapelizod as "painstaking" in its detail and say they will continue searching for as long as necessary.