We hear much about the Irish in Bede's History. St. Brendan is not among those listed, unfortunately, but the others who are mentioned must have been sailors anyway, although the voyages they take are not necessarily nautical. This link will help you correlate geographical and political information.
First, the political. We know that the Irish represent division to Bede (among other things), as opposed to the unity of practice and observance he prized. Who are Bede's major Irish figures? Think of Aidan and Fursey for starters (Drihthelm was not Irish, by the way). Check the index to our translation of Bede's history and make a list of these characters and what their individual lives represent to Bede.
Next, the geographical. What is the "point of entry" for the Irish into England? It appears to be Iona, the small island off the northwest coast of Scotland--indicated on the maps in Image 1 and Image 6 in this module.
If you want to take another direction and read about St. Brendan--a celebrated character in Irish myth and history--read on.
St. Brendan was born in Ireland near the end of the fifth century (c. 484). He famous as the hero of the extraordinary story of "The Voyage of St. Brendan," which reports only one of the two voyages said to have been made by the saint. His voyage is usually said to be a prime example of the medieval practice of "peregrinatio" (or pilgrimage) "pro amore dei" (for the love of God). According to the Irish version of this custom, the saint left his or her native land freely and in so doing became a soldier for Christ by joining in the battle for Christian souls. The voyage, therefore, participates in two key metaphors: it is both a navigational exploit, a journey into an unknown place, and a quest that involves battle. It is both a form of hagiography and a kind of romance or adventure literature. To get started learning about St. Brendan, read the translation of his voyage by J. F. Webb in Lives of the Saints. (Penguin, 1965).
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