Well organised from beginning to end.
Not cheap but definitely worth the money.
Unique experience.
Quite a distance to travel to Doubtful Sound - but it is an enjoyable and informative journey, bus drivers give interesting & informative commentary.
We were picked up by coach from Queenstown and drove for nearly 2 hours through picturesque & rural countryside with a short coffee stop at the half way point. Good coffee.
Arrived Lake Manapouri to take 45 minute boat trip across to West Arm. Lake Manapouri has a warm tourist centre with take-away shop underneath, perfect to keep cosy while waiting for boat to arrive.
After crossing Lake Manapouri we transferred to another coach to climb alpine route of Wilmot Pass. We had a short stop for photos at top of Pass before descending down to Deep Cove. The Fiordland Navigator was waiting to take us on our cruise. All the crew were brilliant from beginning to end. The skipper, the nature guide, chef, cabin crew made the cruise as relaxing or as adventurous as each individual required.
Some of our group chose kayaking & a short cold swim in the Sound, others opted for a small boat cruise to see the shoreline close up.
Although cold & breezy outside, was warm & welcoming inside.
Our double bed with ensure cabin was tiny but comfortable.
Wide variety of food & more than you could eat for both dinner & breakfast.
Highly recommend this tour.

We were lucky to travel over on a fine day, and not much wind. The captain of the vessel was able to provide a commentary and points of interest to us as we travelled over. The catamaran was clean. Staff at both terminals provided excellent service.

We did the crossing in springtime, but the weater had been really bad for a few days. We were told by numerous people "you'll have a rough crossing" and we didn't really know what that entailed.
First of all, when we got to the ferry many of us were surprised that it wasn't really a ferry. You know, the kind that carries cars and trucks. It's more of a boat. It only carries people, and luggage obviously.
Our journey started off smoothly, but very quickly turned into a rollercoaster. The waves were massive and at times we felt like we were flying. A few of our group that tended to get motion sickness were not happy, but the staff were very helpful in suggesting what to do and handing out cloths of cold water. Even people who don't normally feel sick at sea were feeling a bit rough by the end of the 1 hour journey. The main thing is that the staff is friendly and helpful.
Our crossing to go back the next day was much smoother and even the people prone to motion sickness felt fine.
I think it very much depends on the day of crossing so you can never be sure what kind of waves you will get.
Forget about doing a bunch of extreme sports in NZ, just get the ferry on a windy day. That's all the adrenaline you'll ever need!