Red Breasted Merganser

Female Red Breasted Merganser, Mergus serrator, is a diving duck. I've actually seen multiple mergansers act in concert to herd fish in the shallows, their bodies just under the surface of the water. They catch the (slippery little) fish with their serrated beaks (hence the name). They also eat aquatic insects, crustaceans and frogs and are reputed to fly in level flight at up to 80mph, one of the fastest birds in level flight. Note that Raptors such as hawks and eagles achieve their speed in a dive, not in level flight.