Wow! I’d never heard Johnny Cash’s cover of the Beach Boys’ Sloop John B ... one of my favorite songs. Thanks for posting!
Beach Boys covered the Kingston Trio. Possibly the Beach Boys heard it via Dick Dale, King of the Surf Guitar, who also had a somewhat popular version prior to BB.
The song goes back at least a hundred years and was popularized by poet Carl Sandburg.
Very compelling song.
Sloop John B--Blind Blake Higgs (1952)