The steep slopes of Doubtful Sound 9 New Zealand When Capt Cook arrived off the entrance to this magnificent natural fiord, he considered it dangerously narrow for navigation. So he decided not to enter. He marked it as a 'doubtful harbour' on his map, and the name has stuck. It is said that, in those days, the noise of the dawn chorus was so loud that it could be heard from some distance out at sea. Up close, apparently, the bird-song was so deafening that you had to raise your voice to be heard. These days, silence reigns. One of the most moving moments of our cruise was when the crew shut down the engines in a side arm of the fiord. 150 people listened without a word for several minutes to what our tour guide described as the 'sound of silence'. Terrible damage has been done to the indigenous population by introduced predators such as the stoat and the possum - public enemy number one in New Zealand.