As a hint, here's a close-up of one of these li'l critters (maybe not the most common type):
Answer: Ducks! Such as this Muscovy duck from which the close-up was taken (what an odd-looking fellow). Diving ducks dive (duh); dabbling ducks are the ones that dip their heads while lifting their tail feathers.
Bottoms up to yesterday's two solvers, Hazel and Carl. And to whoever submitted the unsigned answer "strawberry", you made me laugh.
