Milford Sound is a fifteen-kilometre fiord in the southwest of New Zealand's South Island. Its walls rise sheer from the water, more than 1,200 metres of them, and it rains about 182 days a year — more than six metres of it. Those numbers are the reason to come rather than a warning. Every heavy downpour sends hundreds of temporary waterfalls over the rim at once, running the full height of the cliffs, and within a few hours of the sky clearing they are gone again. Two of them never stop. A boat noses in under Lady Bowen, 162 metres near the head of the fiord, and on a windy day the spray comes clean across the deck. The same boat runs the full length out to where the water meets the Tasman Sea. The swell that picks up at the mouth explains something: Cook sailed past this entrance twice without seeing it was there. At the head stands Mitre Peak, 1,692 metres straight up from the water, and on a windless morning the whole pyramid appears upside down beneath it.
Guided kayaks leave the head of the fiord early, while the surface is still flat, and sitting a few centimetres above the water you get the walls at their true height, which no deck can give you. The falls are loud long before you reach them. Fur seals lie on the rocks along the waterline, and bottlenose dolphins come in to ride the bow waves. Rare Fiordland crested penguins come ashore in July to nest, their chicks out on the rocks by spring. Then there is what the rain does underneath. All that runoff leaves a permanent layer of fresh water on top of the salt, stained dark by rainforest tannins. It blocks so much light that ten metres down here is as dim as seventy metres out at sea. At Harrison's Cove a floating observatory lowers you into a round chamber to look at it: black coral, which almost everywhere else means a deep dive, growing just under the weather.