My friends and I left Christchurch the afternoon before
We drove to the lake heron car park and hiked in to double hut which took about 1 1/2 hrs. There is one river crossing about 15 mins before you get to the hut.

The next morning we started at 5 and walked up the swim river, crossing it quite a few times.
Once at the obvious ridge we slowly made our way up leaving our wet trainers behind. After one hour of steep scrambling we've had to put on crampons. I highly suggest an very early start as firm snow and ice make the hike much more enjoyable. Great views from the top.