Here are great reference photos for waterfowl.  Different species, different poses.  The first three links have lots of photos.  They take awhile to load, but they are gorgeous, calendar-quality photos when they do. 
We are providing links to these artists' pages to give them due credit.  They are all copy-righted, and are available for personal viewing only.

http://www.4co.us/Ducks-Unlimited-Waterfowl-Pictures.html

http://www.4co.us/Goose-geese-Waterfowl-Photography.html  
( this site has great reference photos of a lot of different species)

http://www.pbase.com/madmedic/ducks&page=39
57 pages of ducks!

http://www.lookoutnow.com/feeder/wood_01.htm

http://www.photosig.com/go/users/viewportfolio?id=135146
(great, clear action duck photos)

photos.jibble.org/ KennetandAvonCanal/duck_landing

http://www.rarebird.org/forum/uploads/BrianZwiebel/2005-03-15_061823_Pintail_Pair_Landing_Mallard_Club_March_MG_3817.JPG

www.quack-o-rama.com/