http://www.wdwinfo.com/wdwinfo/hours.htm#water
The Electrical Water Pageant usually follows this schedule:
Disney's Polynesian Resort - 9:00pm
Disney's Grand Floridian Resort & Spa - 9:15pm
Disney's Wilderness Lodge - 9:35pm
Disney's Fort Wilderness Resort & Campground - 9:45pm
Disney's Contemporary Resort - 10:05pm
Magic Kingdom park - 10:20pm (only during extended Magic Kingdom Park hours)
(You may want to check with the resort just in case the schedule changes or if its canceled due to the weather that day)