Prime Minister Narendra Modi commissioned the first made-in-India Scorpene class submarine INS Kalvari into the Indian Navy in Mumbai on Thursday. Touted as India's deadliest submarine, the attack submarine was indigenously built at Mazgaon Dock Limited in Mumbai in September this year. For the last 120 days, the vessel was put through extensive trials and tests. Kalvari is the first of the six Scorpene-class submarines handed over by shipbuilder Mazagon Dock Limited. Kalvari is named after a deadly deep sea predator of the Indian Ocean- tiger shark. The first Kalvari was commissioned on December 8, 1967 and was also the first submarine of the Indian Navy.