Either a period on duty, or a detachment of crew members acting as a unit for watch-keeping purposes. Thus one watch (detachment) may take the first watch (first tour of duty), while another watch is off duty and enjoying the ‘watch below’. Although ships normally keep watches of four hours (though with two two-hour dog watches in each 24 to break the diurnal repetition of the same watches!) family crews on small craft usually make their own special routines. (See also: Dog watches)