Design an underwater world filled with friendly, colorful sea creatures like dolphins, turtles, and fish, who are smiling and interacting with a group of young explorers. The children, dressed in imaginative scuba gear, are swimming through coral reefs and discovering treasure chests. The lighting is soft, with sun rays piercing the water from above, casting a magical glow over the scene. Bubbles float up around the characters, and the background features an ancient, mysterious underwater castle. The camera angle is wide to capture the scope of the underwater world, with the focus on the joyful interaction between the kids and the sea creatures. The art style should be highly animated, with vibrant colors and exaggerated, expressive features on the sea creatures.