Brian, I've hiked the Narrows countless times. I've never done the through hike from the top all the way, but I've day hiked up from the bottom a lot. During normal flow, I've never encountered anything over waist deep water. It is definitely a hike you MUST do before you die, which is why it has unfortunately become so popular. Hike it it May when flows are down and you can avoid the swarms of people. Or wait until September.