The rainbow shark has an elongated, dark black or dark blue body, or a bright blue body. The snout is pointed. The abdominal area is flat. The fins possess red to orange-red coloration. The linear area from the gill cover, the eye, and the mouth has a characteristic brief stripe. Compared to females, male rainbow sharks have thinner bodies with black lines along the tailfins. Males also have brighter coloration. They can grow up to about 6 in (15 cm) long with an average life span ranging from 4 to 6 years.