Check this link out:
http://www.southernalpsair.co.nz/siberia_experience_flight_walk_jetboat.htmlDid this last year and it was awesome. Been to 5 of 7 continents. I'm usually not big on organized day trips got talked into it and this was one of the most memorable and scenic experiences of my life and without a doubt the best day trip I've ever done.
Summary:
They fly you in to a valley in a Cessna and you land on a grass strip. Then the plane takes off and leaves you there on your own. You wade across a cold ass glacier melt river and pick up a trail. Its a 3 hour hike out of the valley where a jet boat comes and picks you up at a designated time and takes you back to civilization.
If you like fly fishing or ultralight fishing there is a spot just upriver from where the jetboat picks you up. I brought along a collapsable POS ultralight rod just for the hell of it. Was throwing a rooster tail inline spinner and fish were tearing it up. Was using 2lb test and failed to land one before the jetboat showed up. One of these days I'm going back with proper gear and going to stay in that valley overnight and fish.
I stayed at a place called RiverRun lodge in Wanaka. Place was awesome.
If you got any more questions let me know.