Shaw Mayer's water rat is recorded near streams, rivers, and lakes in the Papua New Guinea highlands. It has pale grey ventral fur and a short white tip on its tail.
Compared with B. habbema, B. shawmayeri has longer external ears, paler slate-grey ventral fur, and a white tail tip covering no more than one quarter of the tail.
It is recorded near streams, rivers, and lakes; reports describe waterside burrows and a diet that includes aquatic insects and larvae, earthworms, and leeches.
An extinction-risk assessment has not been added yet.