Doubtful Sound is three times longer and ten times less visited than Milford Sound, and many people who have seen both quietly prefer it. Captain Cook named it Doubtful Harbour in 1770 because he was uncertain whether the winds would let him sail out again once he had sailed in — so he never entered. It stayed one of the last explored fiords in New Zealand well into the twentieth century, and even now it keeps that sense of remoteness.
The approach is half the experience. There is no road to the water. You cross Lake Manapouri by boat, ride a bus over the Wilmot Pass through dense rainforest, and only then board a vessel into the fiord — a journey that takes the better part of a day. The extra effort filters out the casual crowds, and the silence rewards it. Captains will sometimes cut their engines mid-fiord and let the place fall completely quiet, the only sound water running off the cliffs.
Bottlenose dolphins live in the sound year-round, New Zealand fur seals haul out on the rocks near the entrance, and Fiordland crested penguins appear near the mouth in winter. Real Journeys runs the standard day trips from Te Anau, including the Manapouri crossing, as well as overnight cruises with cabins aboard the boat. The overnight trips cost more, but the sound at night — far from any light pollution, the stars hard and close above the black water — is the kind of thing you remember for the rest of your life.