Taoiseach Enda Kenny has led tributes to Caitriona Lucas, a member of the Irish Coast Guard who died during an operation off the Clare coast.
The Kilkee RIB (Rigid Inflatable Boat) was involved in a search for a missing man at the time.
The vessel capsized in rough conditions earlier this afternoon and three Coast Guard personnel entered the water.
The two women were recovered from the water and taken to hospital, where Ms Lucas was pronounced dead.
The third person, a man, was recovered from a nearby cave area after an extensive and complex operation.
Mr Kenny said: "I was greatly saddened to hear the tragic news from Kilkee today.
"The heroic work and selflessness of the Irish Coast Guard is well known around our coastline.
"To learn of the death of Caitriona, and of injury to her colleagues brings home the real dangers our rescue personnel face and this awful news casts a dark shadow over people all over the island.
"I want to convey my deepest sympathy to Caitriona's family, her husband Bernard, also a Coast Guard volunteer, and to the wider Coast Guard family."
The Irish Coast Guard said her husband Bernard is also a member of the Doolin unit.
"The Coast Guard extends sincere condolences to Lucas family and all the volunteer members of the Doolin and Kilkee units. The Coast Guard also wishes to thank all the other organisations that participated in today’s search," it said.
Transport Minister Shane Ross has also paying tribute to Ms Lucas, describing her as a women who "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," he said.
"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."
Speaking to Clare FM, Superintendent Brendan McDonagh praised the work of all involved in the rescue effort.
Other coast guards have also expressed solidarity with their colleagues in Clare.
Howth Coast Guard updated their Facebook profile photo with a black armbard across their logo, calling the incident "tragic".
Image: Facebook/Howth Coast Guard
Achill Coast Guard and the National Ambulance Service also paid extended their sympathies:
Tragic news for our colleague in Kilkee and Doolin. RIP.
— Achill Coast Guard (@AchillCGUnit) September 12, 2016
Our thoughts are with our Coast Guard colleagues after tragic events in Clare Ar dheis Dé go raibh a h-anam dílis. pic.twitter.com/mgNqcpl7iU
— National Ambulance (@AmbulanceNAS) September 12, 2016
