Marco was a cadet at Cheiron's Academy. Before coming to the Academy, however, he grew up in a village of fishermen. When he was of age, he was presented with a walking staff carved from a tree that had been planted when he was born. The planting of the tree was a tradition in his village, but the tree being carved into a walking staff was not. That he received the staff instead of a fishing pole was a symbol of honor. It meant that he should go out into the world and become something more than just a simple fisherman.
Along with Iolaus and Lilith, he was sent on an errand from Cheiron to retrieve some scrolls. He leads them on a shortcut through the Dune Sea, a massive expanse of sand. The three of them end up getting quite lost, however, and Lilith almost gets eaten by a sand shark. Marco blames himself for their misfortune, profusely apologizing even when reassured that it wasn't his fault. When Hercules and Theseus catch up to them later that afternoon, Marco rushes to meet them. Hercules sees the sand shark coming up behind him, but the warning comes too late and Marco is pulled under the sand, never to be seen again. Hercules is distraught, blaming himself for Marco's death. After they escape the Dune Sea, he goes to take what remains of Marco's staff back to his village and to tell his family what happened.