Members of the Garda sub-aqua unit have carried out a dive operation to the wreck of the Alize trawler as the search for missing fisherman Willie Whelan continues.

However, it is understood that the depth of the water in which the trawler is lying, and conditions around the seabed, have prevented a detailed examination of the vessel to date.

The Alize sank on the night of 4 January as Mr Whelan, 41, and 65-year-old Joe Sinnott were on their way back to harbour after fishing for scallops.

Mr Sinnott was taken from the sea by the crew of the Rescue 116 helicopter but pronounced dead in hospital.

Mr Whelan has been missing since the tragedy happened.

A major search in the intervening 17 days has involved the Coast Guard, the RNLI, the Naval Service, gardaí, search and rescue helicopters, as well as local boat owners, volunteers and members of the public.

Weather hampered the search at various times, including last week when Storm Brendan hit Ireland.

Navy divers have carried out extensive work in the area where the Alize sank, about nine nautical miles off Hook Head in Co Wexford, to establish the trawler's position.

It is understood Garda sub-aqua unit divers arrived on the scene yesterday and have been using Irish Lights vessel 'Granuaile' as a base.

The LE James Joyce naval vessel is also on standby in the area.