"Thresher" went to sea again on 18 March 1944, departing Pearl Harbor for the central Caroline Islands. She remained on air-sea rescue ("lifeguard") station during American carrier strikes on Truk, bombarded Oroluk Atoll on 11 April, and photographed islands in that group. The boat played "hide and seek" with numerous enemy aircraft and witnessed several American bombing raids on Truk. She sighted only two enemy ships and was unable to attack either, before she returned to Pearl Harbor on 8 May.