HARARE, Zimbabwe — An overloaded ferry capsized on Zimbabwe ‘s Lake Kariba on Tuesday, killing at least 15 people and leaving 27 missing, the national disaster management agency said. An underwater team for search and rescue operations was deployed on the huge lake, which forms part of the border between Zimbabwe and neighboring Zambia. Kariba is the largest man-made lake in the world by volume and was created in the late 1950s and early 1960s by building a dam wall to block the Zambezi River, resulting in a valley slowly filling with water to form a huge lake that’s now more than 200 kilometers (124 miles) long and up to 40 kilometers (25 miles) wide in places.