Hi Kevin,
Theres a few cave divers around alright. Depends greatly on the type of cave though. Sumps, Resurgences or Submarine. The sumps are generally short and nasty, caving skills are required to reach them and the diving is just a tool to reach dry cave passage beyond the sump. A few resurgences in Ireland do offer better diving with bigger longer passage and greater depth. But the visibility is generally very poor due to surface run off. There is some active exploration of some sites in the Gort/Kinvara and Cong regions. Regarding submarine caves (cave passage once dry and now flooded) probably the finest examples are around Doolin, Co.Clare.
Training wise, I'm not aware of anyone offering training in Ireland. Certification offered by agencies diving in the caves of Mexico, Florida and France are generally not suitable for diving in the fresh water caves of Ireland as the conditions here are quite different.
By the way the book by Martyn Farr is “The Darkness Beckons”, an excellent read.
Slan
John