The natural feature that separates the North and South Islands of New Zealand is the Cook Strait. This narrow body of water is approximately 22 kilometers wide at its narrowest point and facilitates maritime transportation between the two islands. The strait is known for its strong currents and winds, making navigation challenging. Additionally, the Cook Strait is recognized for its stunning views and biodiversity, as it connects the waters of the Tasman Sea to the Pacific Ocean, offering a rich habitat for marine life.