Threadfin sand diver have a slender, eel-like body, with grey to pale brown color. They have a horizontal line with paired, bright white spots and bright yellow ventral fins. From the black spot on the front dorsal fin, 3-4 long fin rays extend upwards. Females lack the long fin rays and have a white margin on the black spot of the dorsal fin. When swimming these fin rays are lying down along the dorsal fin. Appears in loose groups. When startled, they will dive into the sand.

Unassessed by the IUCN Red list. Uncommon species.

Western Pacific; from Indonesia to Fiji, the Coral Sea to Southwest Japan. They inhabit sand and rubble bottoms, reef slopes and coastal lagoons of current-rich waters, in a depth range of 10-40 meters.

Sand divers live in harems, with one male fish and up to a dozen of females. They are protogynous hermaphrodites, meaning they change sex from female to male. As soon as the dominant male dies, a female changes sex to ensure offspring.