Take SR 2 east from I-65 about a mile and a half to Rangeline Road, then turn south and go 6 miles to the marsh. Marshes, oxbows, the river itself add up to lots of northern Indiana swampland, which is a lot more attractive than it might sound to some. The river is not exciting, but still interesting to canoe, and there's plenty of room to hike.
Wildlife is abundant, especially birds.
Take a slog through what's left of the swamp that once covered 500,000 acres, before the farmers decided that the land would work better if the river was turned into a ditch. This was formerly a Nature Conservancy property, then a Fish and Wildlife Area, then it was turned over to Lake County. It might be a good idea to give this back to the state before Lake County neglects it to death. Closed to the more innocent forms of recreation during hunting season. Theoretically, the Lake County Parks and Recreation Board.