The Irish Coastguard has named the crew member who died off the Co Clare coast today as Caitriona Lucas.
The Taoiseach has led tributes to the volunteer coastguard.
He said he was deeply saddened by her death, and praised the heroic work of the Irish Coast Guard.
Enda Kenny said: "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. I hope the other members of the team make a full and speedy recovery. Our prayers and thoughts are with them all at this difficult time.”
Ms Lucas died when the Irish Coast Guard Rib from Kilkee capsized while searching for a missing man.
Transport Minister Shane Ross said she was a brave and valiant woman engaged in the most heroic duties: "Such remarkable courage and heroism in the service of others is rarely equalled and never surpassed. On behalf of myself and my Department I would like to extend my deepest sympathies to the family and friends of Caitriona – a woman who made the ultimate sacrifice in her service to others.
The Irish Coast guard has extended its condolences to Ms Lucas family.
Manager of the Irish Coast Guard Declan Geoghegan says its a huge blow for the service:
Two other coast guard crew members were rescued safely in a major operation off the Clare coast.
A female crew member was taken from the water along with Ms Lucas, and is being treated in hospital.
Rescuers were unable to reach a third male crew member for several hours after he became trapped in a sea cave.
Speaking to Clare Fm, Superintendent Brendan McDonagh said the man was eventually winched to safety: