On our trip to the coast I was watching Common Eiders dive. Eiders can dive down to 60 feet to pick up mollusks and crustaceans from the sea floor. The wings are held partly open during dives. Here's a sequence of a female Common Eider diving where you can see this. She plunges downward head first, her wings held open. I love the last photo showing the water pattern of a little V-ridge, where her head and wings have broken the water. It was tricky getting this photo because you cannot always predict the moment an eider will dive. I could have spent the whole day just watching their behavior.