The correct answer is option 2, Kochi. India`s first port-based Special Economic Zone (SEZ) is located in Kochi, Kerala. A Special Economic Zone is a designated area within a country that is subject to different economic regulations and policies aimed at attracting foreign investment and promoting economic growth.

Kochi, also known as Cochin, is a major port city in Kerala and is located on the southwest coast of India. It is one of the largest and busiest ports in India and plays a significant role in the country`s trade and commerce. The port-based SEZ in Kochi offers various incentives and benefits to businesses, including tax benefits, streamlined customs procedures, and infrastructure support. These measures are aimed at attracting domestic and foreign investments and boosting economic activity in the region.

It is important to note that while the other options mentioned in the question (Chennai, Mangalore, and Visakhapatnam) are also major ports in India, they do not house the country`s first port-based Special Economic Zone.