water shrew

from WordNet (r) 3.0 (2006)

water shrew
    n 1: any of several small semiaquatic shrews usually living near
         swift-flowing streams

from The Collaborative International Dictionary of English v.0.48

Water shrew \Wa"ter shrew`\ (Zool.)
   Any one of several species of shrews having fringed feet and
   capable of swimming actively. The two common European species
   ({Crossopus fodiens}, and {Crossopus ciliatus}) are the best
   known. The most common American water shrew, or marsh shrew
   ({Neosorex palustris}), is rarely seen, owing to its
   nocturnal habits.
   [1913 Webster]