SEWN SKIN BOATS
A Curragh. In 1976 Tim Severin duplicated St. Brendans feat of crossing the North Atlantic in a 36 foot boat similar in construction to the legendary craft of the Irish saint. Historians, like anthropologists, have rarely been small boat people. So it would probably surprise them that Celtic voyages to the New World were most likely carried out in the sewn-skin curraghs, not in the larger, faster, and more manoeuvrable wooden planked ships they used to battle Caesar. The small and slow curraghs were able to ride required to cut through the waves. In heavy seas this could mean capsizing, and when a heavy boat capsizes it sinks. The curraghs would not only be less likely to capsize but if they did they would not sink.
From Atlantis in America Navigators of the Ancient World by Ivar Zapp and George Ericson