This is a sea dragon, and the one on the bottom, the blue one, is a juvenile that has not yet swallowed the acid, has not yet taken in the brown-green algae pond scum into its body to give it energy.
Éste es un dragón de mar, y la imagen inferior, la azul, es uno menor que aún no ha tragado ácido, es decir, aún no ha ingerido el alga verde-marrón para dar energía al cuerpo.