You might get more ideas by checking out my webpage, story of my Alaska cruise with hints and pictures...But I have to concur, layers is the way to go with a waterproof top layer.
Check out my guide for first time cruisers http://www.vsn.org/cruise
6/2002 Radiance Alaska
10/2002 Radiance Pacific NW
11/2003 11-Night Eastern on the Brilliance