Well done on setting up a new thread - Panjin is poorly reported on, so it will be very interesting to hear about what you see! The lake you visited sounds like an excellent patch.
Black Scoters are very rare in China, so I suspect what you saw (in your first and second photos) is the Common Coot. They are like black ducks with a white bill and frontal shield. I imagine that many will be passing through right now and some will stay to breed.