The Water Shrew, although small, is the largest of Britain's three species of Shrew (Common, Pygmy and Water). It is also called the Eurasian Water Shrew and is native to much of Eurasia.
It does not live in the water but usually lives on banks beside water and preys on aquatic insects/invertebrates. It is mainly black with a white underside.
The Water Shrew is Britain's only venomous mammal, although unlikely to be able to bite a human or large mammal. They are solitary and territorial.