R.E.M. released their second album Reckoning in 1984 and Harborcoat is the first song on that album. It was not a ska song but it did have that familiar ska upstroke guitar in a few places.
Anytime the band played Harborcoat live it had more of the ska feel to it than the version on the album does...especially in 1984-1985:
When their first album Murmur was re-released on CD in 2008 it included a live version of Harborcoat that showcased the ska sound.
Although it is not a straighforward ska song (I don't think R.E.M. ever did one - please prove me wrong), it is a great song and the best version I found of it was from a show from the Aragon Ballroom in Chicago from 1984:
This download includes 3 versions of Harborcoat - the 1984 Aragon Ballroom version, the live version from the Murmur deluxe edition, and the album version from Reckoning - for comparison (there are many more versions out there and I have a lot of them).
A few of my 'all time favorite songs ever' (there are a million of them) are R.E.M. songs. -Feeling Gravity's Pull, etc. ...but I won't bore you with that. What I will do is tell you that, while Murmur is considered to be their first album, there was an EP in 1983 called Chronic Town which is included in this download, just because. (Carnival of sorts (Box Cars) is one of my aforementioned 'all time favorite songs ever').