From https://researchframeworks.org/maritime/the-mesolithic/#sect...
> Evidence for Mesolithic seafaring includes the colonisation of islands involving long sea journeys, such as Shetland and the Outer Hebrides (Warren 2005), as well as the location of sites on islands involving very difficult sea crossings, such as Ynys Enlli (Bardsey Island) in North Wales, where one must negotiate the treacherous Swnt Enlli (Edmonds et al 2009).
From https://www.sciencedirect.com/science/article/pii/S030544031...
> Tolan-Smith (2008, 151) notes that at this point there is clear evidence for Mesolithic seafaring, with Ireland being occupied along with the Isle of Man, Rhum, the Hebridean Archipelago and Howick on the East coast of England. Thus, as Warren (2005) and Garrow and Sturt (2011) have argued, there is ample evidence for a strong seafaring tradition in the Mesolithic.