Done it three times since 1974...
Last time in 2004 and only from Prince Rupert to Haines...
Ketchikan I figured would be ruined from my last time but it was fantastic!
Two totem parks there--Totem Bight & Saxman at either end of Ketchikan. Lots of neat scenery along the way. Expect rain and bring a polarizer to saturate the greens. Bring a towel to wipe down the mist and rain, no matter what and lots of plastic bags or shower caps for your equipment.
Shooting from the deck of the ferry at probably 12-18 knots, there were few problems except at night when you just cranked-up the iso shot a lot and prayed for something. Bring a tripod in case trip is smooth and it will help for even sharper images or longer shooting.
From deck, you are fine with an 70-200 on digital or film. Even a pano camera like an X-Pan works well for the passing landscape.
If you are shooting the boat, you'll need something wide since most cabins are quite small, to show the accommodations.
If you are lucky, you may see orcas and eagles. Mostly, they will be too far, even for a long lens and then since you are both moving, pray a lot for a sharp image.
If you do go ashore, go lightly with a wide angle and a telephoto zoom and a minimum of two bodies. Definitely expect the unexpected!
Here's a link to my 2004 Inside Passage pix along the Marine Highway. It won't show anything south of Prince Rupert, but you'll get an idea of what's out there since much of the passage is forest-lined bays and shores.
Alaska 1, August 2004 Page 1
The first five pages are Ketchikan or on the way there.
Have a great time and shoot lots of great pix!