The White-throated Dipper

The White-throated Dipper Cincluc cinclus
Vantaa river
Brave the winter predator

From a perch it will walk into the water and deliberately submerge, but there is no truth in the assertion that it can defy the laws of specific gravity and walk along the bottom. Undoubtedly when entering the water it grips with its strong feet, but the method of progression beneath the surface is by swimming, using the wings effectively for flying under water. It holds itself down by muscular exertion, with its head well down and its body oblique, its course beneath the surface often revealed by a line of rising bubbles.
In this way it secures its food, usually aquatic invertebrates including caddis worms and other aquatic insect larvae, beetles, Limnaea, Ancylus and other freshwater molluscs, and also small fish. A favourite food is the small crustacean Gammarus, an amphipod shrimp. It also walks and runs on the banks and rocks seeking terrestrial invertebrates.
The winter habits of the Dipper vary considerably and apparently individually. When the swift hill streams are frozen it is forced to descend to the lowlands and even visit the coasts, but some will remain if there is any open water.

citation Wikipedia