Blue

 is a small blue monster on The Sea Beast.

Throughout The Sea Beast
When Maisie and Jacob began to explore the uncharted island, they came across Blue, a small, gelatinous monster. Blue was initially scared of Maisie, but she fed him food.

Maisie thought Blue was cute and wanted to keep him as a pet. Jacob did not want Blue as a pet and threw him away several times, but Maisie managed to keep him around. Blue travelled with Maisie and Jacob during their trip with the Red Bluster.

Physical appearance
Blue is a small, gelatinous monster with large eyes and small teeth.

Appearances

 * The Sea Beast

Trivia

 * According to art director Jung Woonyoung, the cute factor was essential. The creatures on the monster island were designed to be more lovable.
 * Character designer Shiyoon Kim was inspired by pugs, so Blue has protruding eyes that point outwards.
 * Blue has no bones, so he is squishy. Blue was animated with spheres that crash into each other, and the effects department added the texture of Blue's skin and wobbly Jell-O movement.
 * According to designer Matthias Lechner, it was a little scary to see Blue's animation at first. Blue only started to look appealing once it went through a second pass.