Marco is a terragog, the new leader of the Praedatori after his father, the Duca Armando, was killed. He falls in love with Becca and so does she in Dark Tide, but Becca feels they shouldn't let themselves love each other because she's a mermaid.
Depiction in Books
Dark Tide
Marco and his sister Elisabetta help Becca and insist that they help her get to the Karg. While on a boat Marco bonds with Becca and feelings begin to develop between the two, they push their feelings aside as Marco is a human and Becca is a mermaid.
Sea Spell
Becca goes to the Palazzo in hopes of getting help and Marco appears to have returned to the family home. He helps the Black Fin Resistance to retake Miromara by getting trawlers so that the army could get to the city of Cerulea the same way that the Death Riders had when they'd taken the city.