Hi Megan!
You can view the Electrical Water Pageant from any of the Magic Kingdom area resorts. You can hop on a resort monorail and visit the Contemporary Resort, Polynesian Village Resort or the Grand Floridian Resort and view the pageant from the beach. You can also take a ferry boat those three resorts or sail over to Fort Wilderness Resort and Campground or the Wilderness Lodge and view it from the beach.
Here is a general schedule for the resorts (times subject to change):
Polynesian Village Resort - 9:00pm
Grand Floridian Resort - 9:15pm
Wilderness Lodge - 9:35pm
Fort Wilderness - 9:45pm
Contemporary Resort - 10:05pm
If your schedule allows, I highly suggest visiting Fort Wilderness for
Chip N' Dale's Campfire Sing-A-Long. You can roast marshmallows and meet Chip n' Dale for some fun songs. Afterwards you can head to the beach to catch the pageant. The Sing-A-Long starts around 7pm in the fall and winter and around 8pm in the spring and summer.
Have a magical day!
Leslie