The whale shark has a streamlined body and a wide, flattened head. The mouth is transverse, very large and is nearly at the tip of the snout. The gill slits are also very large, and are designed as filtering screens. The first dorsal fin is much larger than the second dorsal fin, and is located at the back of the body. The caudal fin is semi-lunate (crescent-shaped) in adults, and with the young, the upper lobe is quite longer than the lower lobe. The whale shark has a unique "checkerboard" colour pattern of light spots and stripes on a dark background.