What the Lonely Planet guide says about Doubtful Sound
Massive, magnificent Doubtful Sound is a wilderness area of rugged peaks, dense forest and thundering post-rain waterfalls. It's one of NZ's largest sounds: three times the length and ten times the area of its better-known cousin, Milford. Doubtful is also much, much less trafficked - if you have the time and the money, there's no doubt (sorry) which one you should visit. Fur seals, dolphins, Fiordland crested penguins and seals are all also occasional visitors to the sound.
Until recently, only the most intrepid tramper or sailor ever explored Doubtful Sound. Even Captain Cook only observed it from off the coast in 1770, saying he was 'doubtful' whether the winds in the sound would be sufficient to blow the ship back out to sea. The sound became more accessible when the road over Wilmot Pass opened in 1959 to facilitate construction of the West Arm Power Station.