Carnival Cruise Line offers "fun ship" cruises. They are affordable and casual so they appeal to families and young couples. Carnival has cruises out of Seattle to Alaska; see the list below.
Carnival cruises is known for youth programs. There are facilities and activities for youths (age 2 to 11) and teens (age 12 to 17). The special Seuss at Sea program offers a character parade, story time, crafts, and a character breakfast.
The Carnival cruise ship in Seattle is the Carnival Legend. See the ship page for information on amenities, photos and video.