The left-back's long-range strike flew into the top corner to break the deadlock in Crosby as Liam Millar, Isaac Christie-Davies and Jack Bearne were also on the scoresheet.
Marine levelled proceedings shortly after half-time but substitute Millar put the visitors back in front when he converted the rebound to his missed penalty.
Christie-Davies then applied the finishing touches to a well-worked move before Bearne added Liverpool's fourth.
Millar completed the scoring with the final kick of the game to grab his second of the day.
Speaking after the match, U23s manager Neil Critchley told Liverpoolfc.