Can you get to the Aran Islands during the winter?
Aer Aran has daily flights from Connemara Airport, near Galway, in December. http://www.aranislands.ie/Inis-Oiir/getting-there-and-around/ We used them and found it fast, fairly cheap, and not as weather dependent as the ferries. Plus, it was a real treat to fly in the tiny airplane, with local people speaking Gaelic behind me!
During the winter the ferries run only infrequently, mainly due to the water conditions. If the water gets rough it can be days at a time before the ferries can run.