Sea lions: Espiritu Santo Island, Mexico

Jacques-Yves Cousteau called Baja’s Sea of Cortez the “aquarium of the world,” and sea lions are undoubtedly its star performers. Los Islotes, the sea-lion colony at the north end of Espiritu Santo Island, is a veritable playground for these friendly mammals — and divers are invited to join in the fun and games. Sea lions birth their pups at Los Islotes in June, and by October these quick learners gain enough comfort and ease in the water to do loops and barrel rolls around divers. The best time to experience the sea lions at Los Islotes is October through June when they’re most playful and visibility averages 50 to 75 feet. Fortunately, development will never disturb these sea lions' playful antics: Espiritu Santo Island is a protected national marine park.