- Began playing guitar when he was 14.
- First two songs that he learned on the guitar: Metallica's "One" and Cat Stevens' "Father and Son."
- Was a pro surfer during high school, but decided to pursue more grounded activities after a surfing accident left him with more than 150 stitches, a broken nose and missing teeth.
- Has made several acclaimed surfing documentaries.
- Met his wife Kim during their first week of college; they were both 18.
- Entered the music business via a circuitous route: a four-song demo tape that he made was passed around the surfing scene. Garrett Dutton of G. Love and Special Sauce, who was an amateur surfer, heard it, liked it and asked Jack to sing one of its songs—"Rodeo Clown"—on the 1999 G. Love album Philadelphonic.
- Is active in environmental causes. In 2004, he and his wife Kim founded the Kokua Hawaii Foundation, which teaches about the environment in schools and communities in Hawaii.
- Patti Johnson — Mother
- Kim Johnson — Wife
- Pete Johnson — Brother
- Moe Johnson — Son
- Leo Johnson — Son
- Jeff Johnson — Father
- Trent Johnson — Brother
- University of California, Santa Barbara, California, United States (BA in Film Studies, 1997)