USS Guardfish (SSN-612), a Thresher-class submarine, was the second ship of the United States Navy to be named for the guardfish, a voracious green and silvery fish with elongated pike-like body and long narrow jaws.

The Permit-class submarine was a class of nuclear-powered fast attack submarines in service with the United States Navy from the early 1960s until 1996. They were a significant improvement on the Skipjack class, with greatly improved sonar, diving depth, and silencing. They were the forerunners of all subsequent US Navy SSN designs. They served from the 1960s through to the early 1990s, when they were decommissioned due to age. They were followed by the Sturgeon and Los Angeles classes.