Is HMS Pinafore an operetta?

One of librettistlibrettistA libretto (Italian for “booklet”) is the text used in, or intended for, an extended musical work such as an opera, operetta, masque, oratorio, cantata or musical.

What kind of ship was the HMS Pinafore?

Pinafore was stricken from the Navy List on 1 July 1920.
USS Pinafore (SP-450)

United States
Stricken 1 July 1920
General characteristics
Type Launch