All but the first 300m of the gorge can be seen from the helicopter; be sure to fly over the gorge and pay attention. The rapids are segmented, and vaguely recognizable from the air. What you can't see (the first 300m) is very committing, tight vertical walls, but manageable, pushy class III white water exists here. Most of this you can see from the swing bridge at the entrance.
Once through the committing section, the walls open up slightly and there is room to get out on the bank/in the river bed to scout/portage. Rapids also get more serious from here down. Some must be paddled, some must be portaged. The atmosphere is fairly intense. Everything seems enclosed, and the water seems confined and powerful.
The rapid at the exit of the gorge is a good indicator of the style of kayaking within the gorge. This rapid is accessible at the end of the Morgan Gorge portage.
The river bed seems somewhat mobile, and there have been differing descriptions of rapids over time. Treat every descent as a first.
Check out video by Dave Kwant http://www.kayaksession.com/wild-and-hidden-places-a-kiwi-classic-kayak-...
For the upstream section, Graham Charles wrote: "‘Don’t go into Morgan Gorge’ the Hot Tip said, I should know I wrote it. I must’ve forgotten as we sat at the entrance to the gorge in January 2002. We had run the river in four hours and arrived at the portage around the gorge in the early afternoon. Flying the gorge it had looked like some good lines existed and some portages around the impossible stuff. Like moths to a flame we were all drawn to the excitement of the unknown. The anxiousness was laughable as we ran the entrance drops and all took a pounding of some sort. Like a lost world the twisting corners kept things hidden, some hard drops, some mandatory portages and we were in up to our armpits. Over half way through before we met our nemesis. A rapid no one wanted to attempt, no way back, no way around. We left the boats and began the climb up the only possible break in the vertical moss walls. We made the cars that night after seven hours of walking and bush crashing. The boats took a further nine hours the next day after we abseiled in and hoisted them out and carried upstream and eventually around the gorge. A great trip - the Hot Tip gets upgraded to a Very Hot Tip."