In 2003, on our first ever cruise, the Zandaam deviated from its scheduled intinerary to make its way up Tracy Arm to the glacier. What a great experience that was. It was so tight in spots it seemed like you could almost reach and touch the walls!
The captain had to go north on the windward side of Island to make up the time needed for that side trip, but the rough seas were well worth it. I don't know how long or how often the cruise lines did that, but it seems that only the excursion boats are visiting now.