Giambastiani's operational assignments included several in which he was responsible for both demanding at-sea operations and the development of new technologies and experimental processes. Early sea assignments included and the s blue crew. While assigned to USS "Puffer", he was a 1973 winner of the Fleet Commander's Junior Officer Submarine Shiphandling Competition. He commanded the NR-1 Deep Submergence Craft, the Navy's only nuclear powered deep diving ocean engineering and research submarine and , where the crew was awarded three consecutive Battle Efficiency "E"s, three Navy Unit Commendations, and two Fleet Commander Silver Anchors for excellence in enlisted retention.