Crew sleep-wake patterns were investigated using the new technology of actigraphy. During a routine seven day coastal patrol in HMCS Saguenay, the devices were worn by 20 personnel; eight dayworkers, eight ‘rotating shift’ watchkeepers, and four senior crew. To assess the validity of actigraphic data the results were compared with subjective sleep reports. Analyses showed that the actigraphic estimates of sleep quantity exceeded the subjective estimates by about one hour for watchkeepers and senior crew. There was no difference between the two estimates for dayworkers. Reasons suggested for differences between actigraphic and subjective sleep quantity estimates are discussed. Further laboratory studies are required to determine threshold sleep values for the actigraph. Once these studies have been completed the actigraph will have great utility for helping to determine optimal work/rest/sleep regimes for operational environments.