The explorer credited with discovering the Pacific Ocean is Vasco Núñez de Balboa. In 1513, he crossed the Isthmus of Panama and became the first European to see the ocean from the New World, naming it the "South Sea." Balboa's expedition was significant because it proved the existence of another ocean and opened up the possibilities for exploration and trade routes. His discovery paved the way for future European expeditions into the Pacific region and contributed to the European understanding of the geography of the Americas, fundamentally changing global trade patterns.