source
"It is an extraordinary project that involves building a 64 km dam and turning a part of the Arabian Sea into a freshwater lake. It will take at least 20 years to build and if it ever gets off the ground, it will cost around Rs 50,000 crore (Rs 500 billion)."
cost : Rs 500 Billion
benefits:
2,000 sq km freshwater reservoir 5,880MW of tidal power
irrigate 1,054,500 hectares of land
reclaim 1,100 square kilometres of saline land