Hours: Great Falls trip departs Sat.-Sun. at 11, 1:30 and 3, Apr.-Oct. (also Fri. at 11, 1:30 and 3, June-Aug.). Williamsport trip departs Thurs.-Sun. at 11, 1:30 and 3, Memorial Day weekend-Labor Day weekend. July-Aug. trips may be cancelled in the event of hot weather and low water level. Phone ahead to confirm schedule.