Located in Fiordland National Park, it is one of New Zealand's scenic highlights. it was incorrectly named a sound, as it is a fiord. A fiord is a valley which has been inundated by the sea, as the result of glaciers eroding the valley floor in the past, below todays sea level.
Milford Sound is the most accessable of 14 fiords and arguably the most spectacular, although many think that Doubtful Sound is even better. It is certainly much bigger, but is harder to reach.
Boat trips on Milford Sound take you out to the Tasman Sea and back. The trip passes many spectacular waterfalls falling from huge cliffs. The boat gets close enough to some waterfalls allowing you to hold a cup in the air to collect what is known as the world'scleanest water. Seals can be seen sunbathing on the rocks and dolphins often ride the wake of cruise boats that travel through here.
Milford Sound is certainly a visible spectacular work of nature but what is not obvious is what lies beneath the water. The first few feet of water in the fiord is darker fresh water which is runoff from the melting snow on the mountains that flows through lush rainforest and down the steep cliffs into the fiord. Below that layer of fresh water is the salt water of the Tasman Sea. This unique combination of fresh and salt water tricks deep sea plants in to growing closer to the surface than otherwise and this provides divers are rare opportunity to see them. Divers can also be rewarded with a rare black coral that is unique to this area.