The Irish Whale and Dolphin Group has said over the past year it has validated up to 200 sightings of a pod of three bottlenose dolphins along the Dublin/Wicklow coast.
The sightings offer further evidence that the animals may now be resident in the area.
Analysis of the sightings shows the dolphins rarely travel north beyond Dalkey Island, or south of Wicklow town, indicating a core range of 33km.
The IWDG said there are three "very obvious sighting clusters" in Killiney Bay, Bray Harbour and Greystones Harbour-Kilcoole.
Despite one of the three animals having a very well marked dorsal fin, they have not so far been matched outside of the Irish Sea.
Last October, one of the dolphins was photo ID matched in Kilkeel, Co Down.
The IWDG said it is very likely that they have been photographed in other areas as well.