Jess is a Wanderer headed off to Doubtful Sound with Real Journeys. This sound has to be accessed by crossing Lake Manapouri, taking a bus along a single track road and finally arriving at the start of the fiord. Definitely not for the faint-hearted!
The particular trip that I found myself on was an overnight expedition aboard the Fiordland Navigator. The itinerary involved sailing down to the Tasman Sea, seeing a seal colony, watching some playful dolphins, splashing around in a kayak and enjoying some delicious food along the way.
I would absolutely recommend this trip to anyone considering seeing one of New Zealand's sounds. It's a $500 trip if you choose to bunk with three other people. Not a bad deal, especially if you stock up on plenty of cake and go for at least seconds or thirds at the breakfast and dinner buffets.