Why in news?
Garden Reach Shipbuilders and Engineers (GRSE), Kolkata, delivered Amini, an Anti-Submarine Warfare Shallow Water Craft, to the Indian Navy on 5 November 2026. The Ministry of Defence announced the handover the following morning. The ship combines sonar, anti-submarine weapons and waterjet propulsion for tasks in coastal waters.
The task: finding an underwater threat
Anti-submarine warfare (ASW) involves detecting, locating and responding to submarines. A submerged vessel can be difficult to observe from the surface. Sound provides an important way to gather information underwater because it travels farther through water than light and radio waves.
Sonar uses sound for underwater detection. An active sonar sends out a sound pulse and receives the echo reflected by an object. The time taken for the signal to travel out and return helps estimate distance. The return journey matters: the measured time includes both parts of the path.
A passive sonar listens for sound already present in the water, such as noise from machinery or propellers. Operators analyse received sounds to help detect and track their source. Active and passive systems therefore obtain information in different ways: one uses transmitted pulses and returning echoes; the other listens for incoming sound.
The Defence Ministry lists lightweight torpedoes, indigenous rocket launchers and sonars among Amini’s equipment. Sensors provide information about an underwater contact, while weapons provide the means to engage a threat. The release also identifies coastal surveillance and mine laying among the ship’s intended capabilities.
Why draught and propulsion matter
A vessel’s draught is the vertical distance between its waterline and the lowest part of its hull. It helps determine the water depth needed for navigation. A shallow-water craft is designed for operations where available depth is an important constraint.
Amini uses waterjet propulsion. In a typical waterjet, water enters through an inlet beneath the hull. A rotating pump impeller adds energy to the flow, and a nozzle directs a fast stream towards the stern. Accelerating water backwards produces a forward force on the vessel.
Steering equipment changes the direction of the jet. A reversing mechanism can redirect the stream to produce force in the opposite direction. This arrangement places the pumping machinery inside the vessel and supports manoeuvring in shallow water. These are general operating principles of a waterjet system.
Building the ship in India
The ministry says Amini was designed and built indigenously, with more than 80% indigenous content. It was constructed to the classification rules of the Indian Register of Shipping. Such rules provide technical requirements against which a vessel’s design and construction can be assessed.
Shipbuilding brings together hull construction, propulsion, electrical systems, sensors and weapons. Integrating these parts means making them work together on a single platform. The delivery marks a stage in that industrial process and in the Navy’s acquisition of coastal-warfare craft.
The island behind the name
Amini takes its name from an inhabited island in Lakshadweep, off India’s southwest coast in the Arabian Sea. The island lies between Kavaratti to its south and Kadmat to its north. The ship also carries forward the name of an earlier Petya III-class anti-submarine corvette, decommissioned in 2002.
Conclusion
Amini’s delivery connects domestic shipbuilding with coastal naval tasks. Understanding sonar, draught and waterjet propulsion explains how the craft’s equipment and design support its intended role.