The flying 22-year-old scored the first hat-trick of his NRL career, producing a sensational diving finish for one try and displaying fantastic hands for another at Bankwest Stadium.
Canterbury threatened to pull off a comeback at the death after Christian Crichton scored an intercept try, but Cronulla scrambled desperately to secure their second win of 2020.
Sharks coach John Morris shook his head in disbelief at Katoa's brilliance post-match.
"He's just such a great kid, Sione. He's worked so hard on his game," Morris said.