A streamlined body and a depressed, broad, and flattened head characterize the whale shark. The mouth is transverse, very large and nearly at the tip of the snout. Gill slits are very large, modified internally into filtering screens. The first dorsal fin is much larger than the second dorsal fin, and set rearward on body.
The two lobed caudal fin (tail) is semi-lunate in adults; in small juveniles the upper lobe is considerably longer than the lower lobe. The whale shark has a unique “checkerboard” color pattern of light spots and stripes on a dark background.