Lady Cosima, or Coco, used to be a lady of Serafina's court and is now a member of the Black Fin Resistance. She has a pet shark named Abelard, or Abby and is Lady Elettra's sister.
Appearance
Coco has long blonde hair and a bright bronze tail. In Deep Blue, she wears a blue tunic and her hair in a thick, long braid down her back. In Rogue Wave, she enchants her tailfins black. For Serafina's betrothal she wears a pink dress.,
Deep Blue
Coco, a lady of Serafina's court, is first seen in Serafina's antechamber, discussing Alithea with Baronessa Agneta. She then questions the baronessa about the Dokimi, only to receive the same answer; because Merrow decreed it. When her sister, Lady Elettra, calls her to try on her gown, she darts off, declaring that gowns are boring.
Rogue Wave
During the attack, she hides in the Ostrokon for four days before she goes to the TideSide. There, she meets Fossegrim and joins the Black Fin Resistance. She enchants her tail fins black to match Fossegrim’s.
Coco captures Sera and then releases her when she is not a death rider. She volunteers to help Sera go get the conches on Merrow’s Progress, along with her pet sand shark Abelard, or Abby.
Coco later turns up to rescue Sera from Marie Therese, the infanta of Spain. Sera stops breathing and Coco begs Mahdi to help her.
She serves as bridesmaid and flower girl at Mahdi and Sera’s betrothal.
Dark Tide
Coco goes out to gather food with some Black Fins,but two are capured, so she races back to the Black Fin's headquarters and tells Serafina.
Sea Spell
Coco is shocked to find out that Sophia is a traitor to Vallerio. She is the first to leave the room after Sera arrests Sophia. In the Southern Sea, Astrid captures Coco and brings her to Orfeo. Orfeo threatens to let Astrid kill Coco unless Sera brings him the talismans. Sera, defeated, gives him the talismans. After Orfeo uses the talismans to unlock Abbadon's prison, he puts the talismans into a box and gives it to Astrid. Astrid throws the box to Coco and tells her go swim away, revealing that the whole capture was a hoax. Coco hides in a cave for the rest of the battle. At Sera's graduation, she congratulates Sera and gives her a bouquet of sea roses. Her parents and Elettra are freed from the prison camps.
Relationships
Serafina
Coco seems to think of the Princepessa di Miromara as something of an idol. She looks up to Sera and thinks she is clever and beautiful.
Abelard
Abelard, or Abby, is Coco’s pet sand shark. She trusts Abby to sniff out death riders as he is very sensitive.