From Wikipedia:
The "Mingulay Boat Song" is a song written by Sir Hugh S. Roberton (1874–1952) in the 1930s. The melody is described in Roberton's Songs of the Isles as a traditional Gaelic tune, probably titled "Lochaber". The tune was part of an old Gaelic song, "Òran na Comhachaig" (the 'Creag Ghuanach' portion); from Brae Lochaber. The song describes fishermen sailing homeward to the isle of Mingulay where their families wait
A long list of performers have covered the song, but the most notable version may belong to The Corries.