Miami chose a local product from American Heritage High School in Plantation, Fla. The 5-foot-11 infielder has an above-average arm and good speed. Listed at 165 pounds, Seymour makes contact with the ball but isn't very strong.
The Draft concludes on Saturday, with exclusive coverage of Rounds 11-40 beginning on MLB.com at 1 p.m. ET.
In a workout for Miami, Seymour displayed skill at shortstop, despite never playing there in the past. He also showed Miami top-of-the-scale speed -- so much, in fact, that he's projected to be a successful basestealer.
Seven of the Marlins' top 10 picks were chosen from high schools.
Maria Torres is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.