The Right Shoes
Day trips on shore are one of the most popular activities on Alaskan cruises, visiting towns like Ketchikan and Juneau. Many cruisers do not anticipate putting quite so many miles in on their feet, however, and do not pack appropriate footwear. While sneakers or running shoes may offer comfort, they do not lend themselves to trail hiking, which will also be available. If you only plan to take one pair of shoes, take light boots or trail shoes.
All cruise ships offer heated swimming pools as well as hot tubs. In the summer and the early fall, the sun can make the days on board quite comfortable. Many people don't think of this when they're packing, because they think of the cold of Alaska, and so they have to buy an expensive swimsuit when they arrive on the boat. Plan ahead by packing your suit, even if you don't plan to use it.
Even in the summer, evenings in Alaska will be chilly. Instead of bringing a particularly warm article of clothing, such as a heavy jacket, plan to layer to protect against the cold. Your top layer should be a waterproof shell jacket, which will also serve you well on day trips and hikes, and your other layers should consist of material such as wool and polypropylene, and not cotton. Long underwear may be all you need in addition to your regular clothes, and it is light and easy to pack.
You may not want to take them with you on shore excursions, but the breathtaking scenery of Alaska is best appreciated with a good pair of binoculars.