One of the two two-hour watches between 4 and 8 p.m. The dog watches permit a shift in the order of the watch every 24 hours so that the same men will not have the same watch every night.
Dog watch, in marine or naval terminology, is a watch, a period of work duty or a work shift, between 1600 and 2000 (4 p.m. and 8 p.m.). It is split into two, first and last dog watches.