Help needed with ID

Ok, I'm going to leave myself wide open to ridicule here, I saw these five chaps and chapettes to the south of the Island on the Roach (I've had to crop two females out of the photo) the males were displaying very elegantly, they were at some distance (hence the poor photo) when I saw the three dark ones I thought it was the three Grebe's i'd just seen down near Paglesham creek with two Shellducks close by, but when I lfted my Bino's I realised they were something different, I'm kicking myself as I should know what they are but can't for the life of me think what!! - I'm a novice to this game you see, it would be much appreciated if someone could put me out of my misery, thanks. BOB