Doubtful Sound – New Zealand’s deepest fjord

Watch out for dolphins in Doubtful Sound.

Doubtful Sound is the deepest (421 metres) and second longest (40 kilometres) of the South Island's fjords. It is quite untouched by the modern world – with rare corals, plants and sea animals calling the fjord their home. It is not as accessible as Milford Sound, but joining an overnight excursion onboard a boat will see you dine on fresh crayfish scouped out of the water in front of your eyes while passing ancient glacier carved valleys, high mountain peaks and spectacular waterfalls. 

According to Maori legend, the sounds in Fiordland in New Zealand were created by the god Tu-Te-Raki-Whanoa as a safe place from the stormy seas.

When he split open the earth to form Patea (Doubtful Sound) four young sea gods helped him by using their adzes to cut the four arms of the sound – Deep Cove, Hall Arm, Crooked Arm and First Arm. Doubtful Sound is 10 times the area of the more well-known Milford Sound, and is the playing ground of bottlenose dolphins, fat New Zealand fur seals and the Fiordland crested penguin to name a few.

The fiord was originally named Doubtful Harbour by Captain James Cook, who sailed past it in 1770. He didn’t sail into the inlet because he though it looked a bit tight for safe manoeuvring (hence the name). It was later named Doubtful Sound by whalers and sealers, although technically it is a fjord.

Like other fjords in the area, Doubtful Sound contains two distinct layers of water that don't mix: the top few meters is fresh water, fed by runoff from the mountains, and below is a layer of salt water from the sea.

The top layer is darkened by the forest tannins, which makes it difficult for light to penetrate. So many deep-sea species such as red and black coral, colourful sponges and sub-tropical fish live in quite shallow depths in the sound. The rare corals can be found 10 metres deep here instead of the usual 30 metres that you will find elsewhere.

Some 10,000 years ago a mighty ice-age glacier extended over the region, and its grinding power as it slid towards the sea sculpted the landscape’s deep valleys. As a consequence there are some amazing waterfalls in Doubtful Sound as rains on the piecing mountains plunge down to the sound, particularly during the wetter seasons. In the Hall Arm, the Browne Falls cascades 619 metres; Helena Falls at Deep Cove tumbles 220 metres.

Tours to Doubtful Sound depart from Manapouri and involve a very scenic bus trip across Wilmot Pass. When you reach the fjord, you can explore in a sea kayak or join a water cruise with one of the local operators.

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