Update 2pm: The Department of Transport has launched an investigation to establish the circumstances surrounding the death of volunteer coastguard Caitríona Lucas yesterday.
In a statement, Minister for Transport Shane Ross said Caitriona "made the ultimate sacrifice" in her service to others.
"Caitriona was a member of that extraordinary group of men and women who dedicate their skills, time and passion so that others may be safe on our coastlines.
"This is an appalling tragedy; the loss of a brave and valiant woman engaged in the most heroic of and unselfish of duties.
"Such remarkable courage and heroism in the service of others is rarely equalled and never surpassed."
Coast Guard manager Declan Geoghegan told Newstalk Breakfast that there is always a "degree of trepidation" every time a rescue team is sent out.
He said: "They were in the last leg of their search and they had radioed in that they were prepared to return home.
"A couple minutes after that, they broadcast a mayday. Whatever happened in those intervening minutes is what we have to establish."
Update 11.45am: Clare County Council is to open a Book of Condolence in memory of Caitríona Lucas who died while on a rescue mission with the Coast Guard yesterday.
The book will be opened at 2pm today at Clare County Hall in Ennis and Councillor Bill Chambers expressed “deep regret at the very tragic loss" of Caitríona who was employed by Clare County Council.
Councillor Chambers said: “I wish to extend the sympathy of the elected members and the people of Clare to Caitríona’s husband, Bernard, their children, Ben and Emma, and her family."
Pat Dowling, Chief Executive expressed his condolences to Caitríona’s family on behalf of local authority staff whose thoughts and prayers are with her family following their very sad loss.
Caitríona worked for the Clare County Library Service for 16 years in the branches at Ennistymon, Corofin and Lisdoonvarna.
Helen Walsh, County Librarian, paid tribute to her saying: “This is a particularly difficult time for the Library service, who recently lost another colleague.”
The library at The Square in Ennistymon will also open a Book of Condolence from Wednesday at 10am.
Earlier: Investigators are hoping to discover exactly what led to the death of Coastguard volunteer Caitriona Lucas, who drowned off the coast of Clare yesterday.
The 41-year-old is the first ever Irish Coastguard volunteer to die during a rescue. It is thought a freak wave hit her boat.
Ms Lucas was on a rigid inflatable with two colleagues. They had gone to sea in testing conditions off Kilkee in a search for teacher David McMahon, from Lissycasey, Co Clare who went missing on Friday.
The two other crew members -Jenny Carway and James Lucy - were airlifted to safety, and are recovering in hospital today.
Mother-of-two Ms Lucas, 41, lived in Liscannor with her husband Bernard, who was also involved in Doolin Coast Guard.
Kilkee Marine Rescue Service member Manual De Lucia knows both survivors of the tragedy, and said locals were shocked by the news of Ms Lucas' death.
"The whole area devastated. We're a very tight-knit community here and everybody looks out for everybody else.
"It's so tragic. It'll take a long time to get over this."