MRY907 Loc: Juneau, Alaska

As a long time Alaskan i usually have my wide angle with me - there are some really good nature photographers here and you can buy or access much better wildlife photos than most of us normal people can take (they have planes, boats, cabins, access and time - probably better camera toys too). Most of your best shots will be scenery, people and historical stuff.
Don’t forget to put the camera down and have fun!!!
MikeY

mikegreenwald Loc: Illinois

Most commercial boat travel tends to be in the inside passage, with calm water. Still, the machinery driving the boat causes vibration, so hand holding is needed, and of course image stabilization of the strongest you can find.
I've travelled extensively in the interior as well as on the water including the Aleutians, and if you get that far NW, the water may be VERY rough. For the most part a single lens in the common range of 24-105 is suitable. Occasionally birds and wildlife call for a long zoom, and then even a 400mm lens is likely not enough.
Best wishes for and enjoyable and safe trip!

scsdesphotography Loc: Southeastern Michigan

I went to Alaska some years ago. It has so many scenic vistas you'll have to force yourself to put your camera down. I brought my 11-16 wide angle lens and an 18-200 lens. I used the 18-200 almost exclusively. In Denali National Park the ranger pointed to the rocky side of a nearby mountain peak and said, "that's a family of Dahl sheep up there." I could not see any animals from where I was at but I zoomed to 200 and pointed the lens to where the ranger pointed. Even through the 200 I could barely see them. But after some judicious cropping in PP I was pleased to see the sheep in perfect focus. I recommend that you use a similar lens, you won't want to take it off!