If you think ducks make for an easy subject to photograph, think again. They will do their best to stay just out of range to prevent you from getting a good picture. And they also have an uncanny ability of knowing precisely when you are about to press the shutter. At this exact second they dive into the depths and who knows where they will surface. These aren't your typical quackers that just stick their butts in the air while they stick their heads under water. No sir, these are the diving variety that will go under and swim for a good distance and surface where you least expect it.
They are smart duckies and know it will take the photographer a moment to swivel the tripod to the new position, compose the picture, set the exposure, get focused and maybe scratch your butt. At the magic moment that you are ready to press the shutter, they are ready to dive again. This little game plays out time and time again. But once in awhile you fool the duck and don't scratch your butt and you get a good picture.
What you are seeing here is a Male Bufflehead. The Bufflehead gets it's name from it's over sized head. The early observers thought the head looked like a buffalo. I'm thinking these early observers puffed a bit too hard on their peace pipe. I will say they are a cool duck!