HY-80 is a high-tensile, high yield strength, low alloy steel. It was developed for use in naval applications, specifically the development of pressure hulls for the US nuclear submarine program and is still currently used in many naval applications. It is valued for its strength to weight ratio.
Permit class USS Plunger on the building ways at Mare Island
The Skipjack class was a class of United States Navy nuclear submarines (SSNs) that entered service in 1959-61. This class was named after its lead boat, USS Skipjack. The new class introduced the teardrop hull and the S5W reactor to U.S. nuclear submarines. The Skipjacks were the fastest U.S. nuclear submarines until the Los Angeles-class submarines, the first of which entered service in 1974.
USS Skipjack