Great thread. Here's a few more from Great Big Sea. Saw them in Toronto in '05, awesome in concert.
Great Big Sea
Harbor Lecou (more about fooling around than sailing, but schooner mentioned)
Barque in the harbour
That about covers what I have from GBS that hasn't already been covered. Here's some other stuff:
The seven deadly sins - Flogging Molly
Tobacco Island - Flogging Molly (not so much about sailing, but it's mentioned)
Queen Ann's Revenge - Flogging Molly
For a little island flavor:
Great big boat - Taj Mahal
Also, look up "Newfoundland Sailing Music". There is some really great stuff that has come out of Newfoundland and Labrador, great seafaring tradition. Here are a few examples that I think might fit the genere here:
Santiano - Many artists a good one is Shanneyganock but I couldn't find an online version.
Greenland Whale Fishery - Many artists, my copy is by the "The Celtic Connection"
Rollin' of the sea - Irish Descendants
Theresa Maria - Fine Crowd