How do eskimos hunt?

In my general education class in anthropology in college I saw a film of an Eskimo hunt. The hunter used a spear attached to a rope. Found or made a hole in the ice, and placed a feather on the edge. When a seal was in the area the feather would move since it needs to breath air. He would stand over the hole and when the seal came to the surface he used the spear to kill the seal and then would cut it up to take home.