And the 24-year-old had never set foot on that stretch of water until he showed up for practice four days ago.
"I think I am so limited with what I know about a place I fish the first time, I have to go with what I do best," Fox said.
His strategy, which paid big dividends on the first day of competition, was to hit the river's shallow grassy backwaters that are not so unlike what he was weaned on in Florida.
Fox led the Rumble by 3 ounces over Alabama's Aaron Martens, who put 16-5 on the scales. Grant Goldbeck of Texas was in third with 16 pounds, Arkansas' Billy McCaghren went into the second day in fourth with 15-11, and Gonzales' Greg Hackney was in fifth with 15-10.
Petal's Cliff Pace was 11th with 14-12.
The spread between first and 49th place - the cutoff after Day 2 - was even tighter. Just 3 pounds, 11 ounces separated Fox from 49th place, a position shared by five pros.
Davy Hite of South Carolina, who sat about midway in that Top-49 mix with 13-13, summarized the situation with his on-stage comment: "Ounces are going to be everything."
Fox said he had a five-fish limit within 20 minutes of Thursday's start.
"I got on the right spot that had a good school in it," Fox said.
He stayed put for most of the day, working to improve his bag. He said he caught about 30 fish by day's end, culling several times.
"It's all about the method that catches them," he said, sharing only the detail that his method is probably not similar to any other Elite competitor's.
Martens, the last boat to leave the dock Thursday, said his best spot was "something everybody else missed."
"And I found a second spot like the first, maybe something with a little better quality, some 3-pounders," he said.
By the end of the day, "I was actually shaking them off," he said. The bass were 2 to 2 1/2-pounders - perhaps good enough to save for Day 2 - but they wouldn't have helped him improve his weight Thursday, he said.
"My goal is Top 12, at least, to try to regain a Classic berth," said Martens, whose slow start to the season could jeopardize a 14th trip to the championship.
Goldbeck, with 16 pounds even, said he's sharing his water with two other Elite pros.
"I also have two little sleeper spots, and I tried to sneak in there without them seeing me to try a little something different," said Goldbeck.
First prize in the event is $100,000 and a berth in the 2013 Bassmaster Classic. The pros also will be out to earn points, which count toward a postseason entry and qualification for the 2013 Classic.
The largest bass of the day was caught by Stephen Browning of Hot Springs, Ark. His 4-13 was the first candidate for the event's Carhartt Big Bass award of the tournament, worth up to $1,500.