Coracles were small, usually round boats made of a framework of split and interwoven willow rods or other bendable rods like ash, tied together with bark, then covered in tarred animal skin to keep it waterproof. These were used for centuries mostly in Wales but also parts of western Ireland. Fishermen in two coracles would stretch a net between them to catch fish. Coracle craftsmen still make them today.
That’s not the boat type they are talking about. This is the ocean going currach is.what they mean. This one went from Ireland to North America to prove it could be done with Stone age tech. The First Nations of the far North have a similar boat called a Umiak it too can cross oceans and there is evidence the Inuit people made it as far as the water north of.Scotland in those boat chasing marine mammals. It doesn’t take a large boat to.cross oceans if you have the stones to do it. A German man set out on a Inuit designed kayak he paddled it down river from Germany to the Black Sea out into the Med through the Suez Canal and via the Red Sea into the Indian ocean, he then paddled to India , and cross the India ocean to Sumatra then to northern Australia where he requested to stay they granted it. 20,000+ miles in a kayak so yea humans have been able to cross oceans for at least 50,000 years.