The commonly paddled section is from the outlet of Lake Ada down to the Sound. There are two channels leaving the lake. Take the left one. In very high levels after very heavy rain the river can push into the big class V realm. If you are out of your depth the track is very close to the river the whole way.
Once leaving the lake there is a series of steep rocky rapids in the class III+ range. Be wary of undercut rocks and the odd trapped log in this section. Eventually the two channels join and you will feel the extra water suddenly through a series of big water moves and hydraulics. These lead to a long flat section just above the crux rapid. Scout from the rocks at the head of the rapid. Portage on river right in the slippery moss and big boulders if you need to. A tricky entrance and drop into a cauldron requires some thought, as does the important cauldron exit. The rest of the rapid has many big holes so hold on to your hat and poke ‘n’ hope because you wouldn’t have scouted the bottom.
The final rapids make a fun finish down to the sound and paddle back to Deepwater Basin.
To get to the put-in; take the road to the wharves behind the airport. Paddle directly across the sound to Sandfly Point Hut and jetty. Shoulder boats and wander up the valley. Forgive the amusement of any Milford walkers who happen to see you. Put in at the jetty at Lake Ada. It is also possible to put in at a range of sites up the river, but the walk is not difficult and the run makes up for it.
Due to didymo controls for Fiordland National Park, the Arthur is closed to all watercaft unless a permit is obtained either from DOC in Te Anau or Alan Cosgrove at Fiordland Lobster Company in Milford. no longer under any circumstance can you padde across Deepwater Basin to the river; a boat (Real Journeys) or chopper (Milford Helicopters) is needed. Rosco's Milford Sound Sea Kayaks may also be able to help out with potential boat and or help with permit. Note that if people obtain a permit from Te Anau, you can not get your boat wet before the Arthur. (Blake Reid)