The S-58 was initially known as the HUS-1 Seahorse in USMC service. 516 HUS-1s were produced, each to move 12 fully armed troopers and carried machine guns mounted in the side doors. These were known as the UH-34D after the US designation consolidation. A further 40 HUS-1A (later UH-34E) were then produced as an amphibious version with floats. 7 further airframes were procured in the VIP configuration as HUS-1Z (later VH-34D).