Traditional Irish Music
As Carlos mentioned, it's Arran Boat Song, yes. But in case you seek new-to-you ones, there are some reels that become wonderful slow airs when played at a more stately pace, by the way, experiment a little!
Here's how I do Arran Boat Song with a diatonic harmonica. Did it about a year ago.
"Shaun," That KelticDead Guy.