Rangers in Zion National Park have rescued two hikers who became stranded in the lower reaches of Heaps Canyon after underestimating the difficulty of one of park’s more challenging canyoneering routes. The unidentified couple, a 26-year-old woman and a 41-year-old man, began their hike on Saturday, believing they could complete the course in one day. Their chosen route was about 11 miles long and involved swimming through cold water and a 300-foot free hanging rappel, among other obstacles. Rangers realized that the couple was overdue when they saw their car still parked at the trailhead on Monday. They were rescued by helicopter on Tuesday after completing roughly two-thirds of the hike. "The group also had far less experience than most Heap's Canyon travelers. While canyon hiking (canyoneering) in Zion can be a challenging and rewarding activity, it is not one that should be entered into lightly," park officials said in a statement.