I go to J.W. Pepper for all my choral needs. If you go to their search site here and put "song of the sea" (no quotes) under title and Hannisian under Composer you can even hear a Real Audio clip of the song. A single copy would be very inexpensive to buy, and besides, if you're going to record it you need to buy a copy for every singer.

It sounds like a lovely song!

Allison