We loved the Alaskan cruise!! I wore pretty much the same thing that Mommy C mentioned. I don't remember it being cold in the ship, though. The only time I was really cold was when we went out on the deck while we were cruising near the glacier but totally worth it to see the beautiful scenery!! They had hot chocolate and blankets for us, though. :)
The weather was beautiful the rest of the time. We had light jackets, just in case.
Just FYI, if you think you might get sea sick, take meds with you. I was fine except when we were out in the open water after we left Seattle and when we were heading back to Seattle at the end. The wrist bands didn't work, AT ALL!! I had to go to the infirmary and it cost an arm and a leg for meds!!!