Dolphins are characterized by smooth and hairless skin, gray-black body, gradually changing color from dark gray near the tip of dorsal fin to light gray, gray-black upper and lower surfaces of dorsal fin and caudal fin, basically pure white abdomen, streamlined body, thick and round middle part, gradually tapering from the back of dorsal fin, and obvious uplift on forehead.

Dolphins have typical morphological characteristics of toothed whales, such as spindle-shaped body, single crescent-shaped breathing hole, skull intussusception, backward expansion of maxilla and overlapping of frontal bone, asymmetry of left cranial top, conical or nail-shaped teeth and so on. The most obvious variation is related to feeding organs, such as beak, upper and lower jaws and teeth.

Dolphins are aquatic mammals closely related to whales and porpoises. They live widely in shallow waters near the continental shelf, occasionally in fresh water, and feed on fish and mollusks.