Operations at the crash site of Rescue 116 off the Mayo Coast have wound down for the night.
Naval Service divers have been working to partially raise the wreckage of the Coast Guard helicopter, as they search for Paul Ormsby and Ciaran Smith.
Coastguard spokesman Gerard O'Flynn says dive crews are battling spring tide conditions.
"Somebody described it as trying to dive on a flag mast where a flag is flying at full speed in strong winds," O'Flynn said.
"It is very challenging diving conditions when you are at the max of what you call a spring tide."
The funeral of Captain Mark Duffy will be held on Thursday at 11am at the St Oliver Plunkett Church, Blackrock, Co Louth.
He will then be cremated at Dardistown Crematorium at 2pm.
His body was recovered form the wreckage on Sunday.
Captain Dara Fitzpatrick who was the first crew member recovered, was laid to rest last week.