Marrow made an instant impact at Hampton as a freshman, averaging 15.6 points, 3.0 assists, and 3.2 rebounds per game but struggled with turnovers. He averaged 18.8 points, five rebounds and 5.4 assists per game as a sophomore, leading Hampton to the MEAC title game. He earned First Team All-MEAC honors. As a junior, Marrow averaged 24.4 points, 4.9 assists, and 4.1 rebounds per game, shooting 37 percent from behind the arc. He was named to the First Team All-Big South. Following the season, he declared for the 2019 NBA draft but later withdrew his name. In August 2019, he announced he was entering the transfer portal. However, Marrow later announced he was staying at Hampton. As a senior, Marrow surpassed Rick Mahorn as Hampton's all-time leading scorer during a win over UNC Asheville. Marrow scored 18 points as Hampton lost to Winthrop in the Big South championship game 75-68. He finished his career with 2,680 points, the 27th highest in Division I history. He averaged 24.8 points and 6.5 assists per game as a senior and became the first two-time national Player of the Year as selected by BoxToRow, covering historically black colleges in NCAA Division I. He was named to the First Team All-Big South and finished second to Carlik Jones in conference Player of the Year voting.