Ocean Rescue Division Chief Vincent Canosa told WSVN-TV in Miami that a black bag containing Fernandez's checkbook and four signed baseballswas turned in to a lifeguard at 24th Street -- approximately 1 mile from where the 32-foot boat was found upside down on a jetty off Miami Beach.
Fernandez, 24, Emilio Macias, 27, and Eduardo Rivero, 25, all died in the accident.
The discovery of the baseballs was made on the day that the Marlins returned to the field with everybody wearing black jerseys with the number 16 and Fernandez's name on the back. His teammates honored him in an emotional pregame ceremony, and second baseman Dee Gordonfought back tears as he crossed home plate after hitting his first home run of the season in the first inning.
Fernandez, who had been scheduled to start Monday night's game against the Mets, was 16-8 with a 2.86 ERA this season, earning his second appearance in the All-Star Game. The 2013 National League Rookie of the Year was 38-17 with a 2.58 ERA in 76 career starts for the Marlins.
Fans established a makeshift memorial on the plaza outside the ballpark entrance, leaving dozens of flower arrangements -- daisies, carnations, roses and lilies, the result as colorful as Fernandez's personality. There were also candles, and messages scrawled on balls, balloons, photos and jerseys.
"It's our job to make his life matter, so we're going to do that forever, and forever starts today," Marlins president David Samson said Monday.
The Associated Press contributed to this report.