The 43-year-old Santa Cruz surfer split $50,000 in prize money with the next four finishers -- Alex Martins, Greg Long, Zach Wormhoudt, Mark Healey and Shawn Dollar, the Half Moon Bay Review reported.
It was Mel's first win at the event, which started in 1999.
"I've been surfing Mavericks for 25 years," Mel said. "It's a relief [to win] more than anything else."
Forecasts for 20-footers meant the elite tournament was declared "on" for the first time in three years at the legendary reef break south of San Francisco.
Spectators were kept away from the shoreline to prevent them from being hit by rogue shore breaks.
One big-name surfer watching warm and dry on shore was Kelly Slater, whom organizers said had to pull out Saturday. The tournament said in a written statement Slater had to withdraw due to a conflict with the rules of the Association of Surfing Professionals.
The statement said since Slater is ranked in the ASP top 34, he cannot participate in events that are not sanctioned by the ASP. Mavericks did not apply for a special ASP sanction that would have allowed Slater to take part.