The Indian Navy will kick-start on Tuesday a two-day multi-agency military exercise covering India's 7,516 km-long coastline, involving 13 coastal states and Union Territories, to further bolster maritime security and surveillance, officials said. Billed as India's largest coastal defence drill, the second edition of exercise 'Sea Vigil' is being organised to check the efficacy of the measures initiated to plug gaps in coastal security following the Mumbai terror attack in 2008, they said. "The scale and conceptual expanse of the exercise is unprecedented in terms of the geographical extent, the number of stakeholders involved, the number of units participating and in terms of the objectives to be met," the Indian Navy said.