The marine mammal known for its intelligence and playful behavior is the dolphin. Dolphins are social creatures that exhibit complex behaviors, including communication through a variety of sounds and body language, as well as social interaction during group activities. They are often observed engaging in playful activities, such as surfing on waves, playing with objects, and engaging in cooperative hunting techniques. Some species of dolphins have also displayed advanced problem-solving abilities and self-awareness, which are suggestive of high intelligence. Their playful nature and friendly demeanor contribute to their popularity in aquariums and marine parks around the world.