Portions of the following information were taken from technicaldiving.ie

There's an article in Irish Speleology no14 from May 1991 by Fintan Convery from University College Galway "Locating marine caves using Geophysical VLF-EM Method" Without getting into details that short article described research which was carried out as part of an M.Sc. in Applied Geopphysics and it used Marmaid's Hole as a test site. The idea was not as much to map the cave but to see if the cave could be mapped from the surface. Results were compared with cave diver's survey and were close enough. But what was really interesting was author's note about potential extensive system at the mid point of Boodaun, 150m north of Mermaid's Hole. According to author's research there should be substantial passage striking inland for at least 125m. I looked at the map in "Caves of co. Clare and South Galway" and the only thing down there was Joe's Cave, described as not explored. I found it very strange - not explored? That was hard to believed. With all that effort put to explore Reef Caves, Hell Complex and even Urchin Cave located much further to the north, what would be the reason that site with such theoretical potential hasn't beeen explored? Unless VLF-EM was wrong and there was nothing interesting there....But soon I realised that there might be one more possible answer.According to the map entrance to Joe's Cave was at the north end of Boodaun Bay in the area of very turbulent sea, with very violent surf and surge always present. Sea around Hell or even Mermaid can be calm but Boodaun is always hot spot.