Duck Species

Hi,

We were strolling a long the beach a few days ago, and we saw a dog attack a bird. 

We rescued the bird and took it to a vet to be seen to, and it seemed relatively unharmed, but it was struggling with its wings. The vet promised to take a look and give me an update. 

We were just wondering if anyone knew what kind of bird/duck it is?

 

The closest i have been able to find is a Cayuga duck, but they seem to be green/blue in the light. This duck was jet black! It was so stunning. 

Hope someone can help!