Many years ago before he was born, the Sirenas used to sink human ships. But one day, his father, King Pescoro of the Sirenas, saw a woman named Camila drowning. Feeling guilty, Pescoro saved her by wrapping her in magical kelp that turned her into a Sirena, and the two fell in love. From that day on, the Sirenas never again sank human ships.
Due to Marzel's mother, Camila, being originally human, he and his sister, Marisa, are half Sirena and can turn their tails into legs when they are on land.
Role in the series
Marzel is with his sister and Cuco when they are spotted by the Avalor Royal Yacht, commanded by Naomi Turner's mother, Captain Turner. When Naomi's parents open fire on Marzel, Marisa, and Cuco, Marzel fights back, but just as he's about to use his Sirena singing on them, Marisa points out Elena as she intervenes and destroys one of the Turners' crossbows with the Scepter of Light. Though this gives Marisa pause and belief that maybe humans are ready to accept them since Elena stopped the Turners after they tried to provoke Marzel and Marisa into retaliating, Marzel doesn't believe it, and when Marisa explains things to their parents back at the palace in Coronado, Pescoro and Camila advise she steer clear of the humans, making Marzel feel better they took his side in the matter.
However, later on, not only does she go behind her parents' backs and meet Elena in person, but Marzel is forced to do so himself, revealing that he and Marisa can turn their Sirena tails into human legs when on land due to their half-human blood. After an attempt by Elena to have her cousin, Duke Cristobal, meet Marisa results in the Duke trying to capture Marisa, Marzel rescues her and then reprimands her for her belief that humans had changed for the better, telling her off that humans hate them and always will. However, later on, Marisa discovers Elena drowning and saves her by wrapping Maligras around her torso, thus granting her the ability to breathe underwater without turning her into a Sirena. Marzel is forced to take Elena to their parents, but despite Elena's pleas for a new friendship between humans and Sirenas, Pescoro and Camila refuse. Later, Marzel discovers that Elena and Marisa have been captured by Cristobal, who tossed Elena's Scepter of Light into the water. Marzel recovers it, and after notifying Pescoro and Camila that Marisa was in danger, he is able to convince them and the rest of the Sirenas to come to Elena's aid with intercepting Cristobal's yacht into the sea wall of the palace. After Elena defeats Shuriki for good, she has Cristobal locked up for his treason and forges a new alliance with the Sirenas.
After aiding Elena with defeating Shuriki and forging a new friendship between humans and Sirenas, Marzel is soon told of Elena wanting to hold a ceremony to sign a peace treaty confirming the new friendship and alliance with King Pescoro and Queen Camila. However, there are those who are against it, including Naomi and Pescoro's Captain of the Guard, Daria. She attempts to ruin the treaty signing by allying with the sworn enemy of the Sirenas of Coronado, the malandros, led by their leader, Saloso, by shutting off the Coral Alarms that keep the malandros at bay. However, once they can enter Coronado, Saloso and his cronies destroy the Coral Alarms, take over, and capture the royal family.
Thanks to Elena, the Coral Alarms are restored and force the malandros into retreat. Daria is forgiven for her actions, and Naomi agrees to put her grudge behind her, allowing the treaty signing to go on as planned.
Later lends he learned about Dia de los Muertos from Elena on how they celebrate in Nueva Vista and support to her grandfather who wants to find the magical shield that he had been searching for when he was younger before it and his friends were lost at sea. Thanks to Marzel's help, Elena and Francisco are able to recover it and allow Francisco some closure to his past.
Later on, Marzel arrives to have some fun but have not fully adapted to his human legs yet. Elena shows up to mention she is holding a Royal Retreat in Nueva Vista and suggests that his father attend as well to show the other rulers from around the Ever Realm that the Sirenas is no longer the feared creatures they were in the past. Thinking it is a great idea, They head back to Coronado only to learn from Ocho that Pescoro is in trouble, his tail trapped in a shipwreck that's about to collapse on him. With Ocho directing where to reach, Marzel and Elena are able to free him just in time, but he soon discovers that his tail has been sprained. Back at the palace in Coronado, as Marisa tends to her father, Pescoro learns of the retreat, but with him unable to attend due to his injury, it is suggested to have Marzel go in his stead. Marzel thinks it would be great, but is told by Cuco to try and act differently from his normal self. As a result, when Marzel shows up, he quickly draws concern from Elena about his behavior and clothing, and soon finds himself unable to have much fun in the activities that Joaquin, Raja, and the other kings enjoy. Instead, on Elena's suggestion, he agrees to take the kings underwater to see Pescoro and Coronado. However, when they encounter Cuco, he inspires Marzel to take the kings through the forbidden Maligras Garden, despite his pleas that it is too dangerous. This results in the kings getting their legs wrapped in the Maligras, causing them to be turned into Sirenas, much to their horror. When they reveal what happened to Marisa and Pescoro, the king is furious with his son for what he's done, and Marzel is ashamed of himself for what he let happen. However, he sees a chance to redeem himself when Marisa reveals the Red Avari blossom is an antidote to reverse the Sirena transformation before it becomes permanent on an island some distance from Nueva Vista and Coronado. Using what he learned from the surface, along with Cuco's help, Marzel reaches the island in good time, but when Elena twists her ankle trying to climb up to reach the flowers that contain the antidote, Marzel is unsure of being able to do it himself, but knowing that the Kings need that antidote or they can never return home to their respective kingdoms as they will be Sirenas permanently, Marzel is able to climb up the cliff, retrieve the flowers, and get them back to the kings just in time, returning them to their human selves. He returns to Coronado with Elena and the kings to show he succeeded, and Marisa and Pescoro are proud of him. As a result, Marzel is allowed to spend some more time on the surface with the kings, even if he still is not used to his human legs yet.