The dense short fur on the head, back and sides is greyish-black.

The underparts are dirty white and are sharply demarcated from the dorsal surface.

Sometimes they are tinged with rusty brown or occasionally are entirely dark grey.

There is a white spot just behind the eye and often another near the small, rounded ear which is nearly hidden in the fur.

The Japanese water shrew inhabits mountain streams, small rivers and ponds, preying on benthic organisms, such as aquatic insects, crabs, shrimp, and small fish.