The Moro Gulf is the largest gulf in the Philippines. It is located off the coast of Mindanao Island, and is part of the Celebes Sea. The gulf is one of the country's tuna fishing grounds. The gulf stretches between and is surrounded by the main section of Mindanao on the east, and the Zamboanga Peninsula of Mindanao on the west. The peninsula's majā¦The Moro Gulf is the largest gulf in the Philippines. It is located off the coast of Mindanao Island, and is part of the Celebes Sea. The gulf is one of the country's tuna fishing grounds. The gulf stretches between and is surrounded by the main section of Mindanao on the east, and the Zamboanga Peninsula of Mindanao on the west. The peninsula's major drainage goes towards the gulf.