Deep sea mission underwater vehicle specialised ship hunt critical mineral deposits Indian Ocean; India premier ocean institute sought tenders near seabed surveys delineate locations sulphide deposits futuristic ocean mission; exploration work early as December; polymetallic sulphides near seabed precipitates hot fluids oozing out deep interior oceanic crust; India deep dive Indian Ocean mining critical mineral deposits; latest news on news18.com; Srishti Choudhary