For Disney Cruise Line, deals are rare and for 20% off??? imo, it’s smokin’ hot.
Save 20% off prevailing rates as quoted on Disneycruise.com for Verandah Staterooms with Restrictions (Category VGT) on select 4- to 8-night cruises departing New York on October 2, October 21, October 28, and November 18 2017.
Link
Use Disney’s site to view dates, itinerary, etc., and then book it on reputable sites like Expedia , Priceline , Travelocity or your travel agent. Sometimes there are added incentive(s) to book with them. Or simply book directly with Disney Cruise Lines.