The Harlequin sweetlips, also known as the Clown sweetlips, completely changes its appearance and movement patterns as it grows.
As a juvenile it undulates its body, greatly exaggerating its swimming motions. It does this to mimic poisonous flatworms and thus deter predators.
As it matures, it swims normally and develops many small, dark spots. This fish is a type of grunt, named after its ability to make a grunting noise by grinding its teeth, and then amplifying the noise with its swim bladder.
…You could say that the movement of a baby sweetlips resembles that of a swimming sea hare. Sea hares swim by undulating their parapodia, or flapping their”wings.”