1) Which Cruise Line is best sailing from Seattle?
I have sailed NCL and Princess in Alaska. Of those two, prefer Princess. I have had friends sail Holland America and was told that they were very good too.
2) Are cruises round trip or one way?
Both, cruises out of Seattle are usually round-trip. The one-way cruises usually travel between Vancouver and Seward/Whittier
3) What is the best month to cruise?
Have gone four times to Alaska. Every time traveled in May, all cruises had wonderful weather, just a little cool. Late August into September is when I have heard many complain about poor weather.
4) What is the cheapest month to cruise Alaska?
May & September by far
5) What are must see's in Alaska?
Glaciers...
If I were only allowed to make one trip to Alaska my choice would be one of the one-way trips (Vancouver and Seward/Whittier. For the sights is so much better that the round-trip cruises from Seattle. Only problem is that it is more expensive because of the one-way airfare.