M.Ir.? "rowing out"
The immram is a literary genre in medieval Irish literature, specifically refering to supernatural sea voyages. However, a distinction must be drawn between the echtrae--a journey to the Otherworld--and an immram--a supernatural voyage. For while
one is pagan in aspect, the other is Christian.
It would seem that the confusion is caused by the text Immram Brain, in which the hero visits the Otherworld of Manannán mac Lír. The likely explanation is that the title is a mistake, or a confusion with the similar, Christian story of Saint Brendan, who is thought to have made a voyage to the Blessed Isles. Oddly, while the Latin name for Brendan's voyage is Nauigatio sancti Brendani abbatis, the Irish name is Betha Bréannain "The Life of Brendan"--not the Voyage of Brendan. For more on the confusion between echtrae and immram in regards to the Voyage of Bran, see Echtrae.
Otherwise, the immrama have heavily Christian overtones:
- Immram curaig Maíle Dúin: In which Máel Dúin sails to various islands, seeking his father's murderer. After seeing forty supernatural islands, he heads the words of a priest and forgives the murderer instead of enacting the typical Irish revenge motif.
- Immram Snédgusa ocus Meic Riagla: In which the kinsmen of Colm Cille visit various fantastic islands and preach the gospel.
- Immram curaig Ua Chorra: In which three pirates, baptised as heathens and worshiping the devil, convert to Christianity after a mystical vision of Saint Michael the Archangel. They then repent for their sins by engaging on a supernatural voyage, where they see the usual talking birds and magical islands, all of which is perfectly Christian to the text.
And so, while some have incorrectly described an immram as a voyage to the otherworld, it is not. Instead, it borrows certain elements of the Otherworld to work as a challenge of the faith of the voyager--not as a pagan description of the home of the gods. There is even some speculation that the immrama may have certain "real" islands in them, such as the Faroe Islands, or the Sargasso Sea, of all places.
Dumville, David N. "Echtrae and Immram: Some problems of Definition." Ériu Vol. XXVII. Dublin: Royal Irish Academy, 1976. pp 73-94.
The Celtic Christianity e-Library. http://www.lamp.ac.uk/celtic/AlphaCata.htm. This site contains the above immrama, as well as the Voyage of Saint Brendan.