One of the best parts about going on a cruise is that it's really two holidays in one — an adventurous sightseeing getaway and fun-filled trip on an ocean liner. Because of this, cruising can be expensive, but if you're willing to book your cruise as late as possible, prices can be dramatically lower since the cruise ships don't want empty rooms. This is especially true for Carnival Cruise Line and Disney Cruise Line, whose prices can plummet six to eight weeks before a cruise sets ail to entice people to book.