Why are deep sea creatures found in shallow water in the fiords?
Milford Sound was formed by glaciers. The entrance is narrow and because of the debris which the glaciers pushed forward during the Ice Ages that entrance is also shallow. The result is that the water is comparatively calm and gives a stable environment for the underwater creatures. A further reason is that Milford Sound receives large quantities of fresh water from the high rainfall and the rivers that flow into it. That fresh water does not flow out to sea quickly because of the narrow, shallow entrance. Being less dense than salt water it lies as a layer on top of the salt water. The rain water that flows into the sound has come from forested mountains and has been discoloured by the tannins in the litter and growth on the forest floor. This results in a layer of dark water which covers the sea water and darkens the environment below. This layer varies from one metre to ten metres deep in the fiord, and below it sea creatures can live in a dark environment such as would be found in
