Can you identify these water fowl?

Here are some water fowl I took pictures of on my way home today.  There were 2 large black birds in the water.. have never seen something like this before.  Also curious about the black and white ducks.  I think the last one is a common merganser.
              In answer to my question of identification and friend emailed me:  Apparently the black water fowl are American Black ducks and the ones in the second picture below are common male mergansers.. to me they look so different than the common female merganser, which is in the third picture with the reddish head and crest.  Its amazing how many different varieties of birds and markings there are.  There were 3 common male mergansers and this one female in this one area in Ashland on Sunday, in back of the Thret Shop that sells violins, guitars, and other instruments.  The American Black ducks were also in the same area.