Permit required - New Zealand has a unique system of simple (mostly) backcountry huts that typically have wood/coal heating stoves, plastic-covered mattresses, clean water, and bunkhouse communal living. Space can be limited and permits are required. Check in the DOC offices of major towns for permits. Good information can be also be found here.
A good, flat trail.
Leaving the Coldwater Hut, head south on the obvious trail. Only about a half mile in is the cut-off for the Lakehead Hut to Coldwater Hut Connector. If the Lakehead Hut is your destination and the water is low, you can cross here. Otherwise continue upstream. The trail mostly stays in the lowlands along the edge of the river but occasionally heads into the hills to avoid one obstruction or another. Eventually, you arrive at the suspension bridge that will connect you to the Lakeside Track or you can continue on to the Upper Valley Travers Track.
Flora & Fauna
Lots of cool birds. Bellbirds, fantails, kaka, and Kea parrots, wekas, rock wren and paradise and blue ducks. The area is dominated by the Black Beech trees which produces a sweet liquid that in turn produces a black mold on all the trees. This can cause a smell like sour, rotting apples.