INS Investigator (J15) is the fourth ship in the Sandhayak class, and operates as a hydrographic survey ship in the Indian Navy's Southern Naval Command. Investigator is equipped to prepare marine charts and electronic maps for the Electronic Chart Display and Information System (ECDIS). It can provide humanitarian aid and disaster-management support, and can be quickly converted into a hospital ship; the ship is equipped with an operating theater and associated equipment to deal with medical emergencies at sea.