Lost on 04 JUL 1944 with the loss of forty-nine officers and crew.
USS S-28 was conducting training exercises off Hawaii with the USCGC RELIANCE (WSC-150).
After USS S-28 dove for a practice torpedo approach, USS RELIANCE lost contact. No distress signal or explosion was heard. Brief contact with USS S-28 was made and lost. All attempts to establish communications failed. Two days later, an oil slick was found near where S-28 last submerged.
A Court of Inquiry was unable to determine the cause of the loss of USS S-28.