Trap Pond State Park is a spectacular wetlands park near Laurel, Delaware and, to me at least, seems more like something you'd find in Louisiana or Florida than in rural Delaware. The park preserves what were once extensive marshes in the Sussex County area and is home to tons of bald cypress trees. For those not botanically-inclined, bald cypresses are those mammoth trees with the bulky roots that you see growing out the water in places like the bayou or the Everglades.
Given that Trap Pond State Park is a marshy area, the most popular activities are naturally boating and bird-watching. There's a boat-rental stop on the shores of the pond where you can rend rowboats, kayaks, and canoes for a reasonable daily price and spend the afternoon paddling around the old-growth trees and snapping photos of the herons and egrets in the area. In fact, they even have special water trails like the Raccoon Pond Water Trail set up that take you through some of the more interesting parks of the park before entering the open water at Raccoon Pond. Of course, there are also plenty of walking trails that circle the pond as well.