[4] In 1952, he founded the O'Neill brand while opening one of California's first surf shops in a garage on the Great Highway in San Francisco,[5] close to his favorite bodysurfing break at the time.

[9] An investigation concluded that UC Berkeley physicist Hugh Bradner was the inventor of the wetsuit.

[10][11] In December 1996 he began a non-profit organization called O'Neill Sea Odyssey which provides students with hands-on lessons in marine biology and that teaches the relationship between the oceans and the environment.

[4] O'Neill resided on a beachfront property in Santa Cruz, California, from 1959 until his death on June 2, 2017.

[14][15][16][17][18] His granddaughter Uma O'Neill is a New Zealand-born equestrian rider, who represents that country and holds both New Zealand and American citizenships, she was selected to compete at the 2020 Summer Olympics.