[3] In 2016, Martyn represented Queensland at the Under 15 National Championships and was named best on ground in a premiership winning division 1 final with the Aspley Under 15 side that same year.

[8][9] During the season, Martyn was named as part of a 26-player national under 18 squad to play against VFL side the Casey Demons in a one-off exhibition game.

[24][25][26][27][28] Martyn suffered a stress reaction in his foot upon a return to training in late-May, which saw him unable to participate at either level when the season eventually resumed after an 11-week hiatus.

[29] In early-July and while Martyn continued to undergo rehabilitation on the injury, a virus outbreak in Melbourne saw the club relocated to the Gold Coast.

[30] Martyn remained in Melbourne alongside the club's other junior contingent for the early weeks of that period, before joining his teammates in a second travelling party in late-July.

[31][32] In place of an official reserves competition that year, Martyn took part in unofficial scratch matches against other clubs' non-selected players after his return from injury in August.

[39][40] He was unable to secure a debut in round 1, instead being named as a non-playing emergency for the season opener while continuing to play pre-season matches with the club's reserves side in the VFL.

With elite[49] hands, he is also notable for his defensive running and ability to apply pressure to opposition ball carriers in contested situations.