Indian emperor Chandragupta Maurya had a full fledged navy as early 3rd c. BCE. This is attested & documented not just in Kautilya’s Arthashastra but by Megasthenes (300 BCE) the Greek himself, in his Indika.
The Mauryan navy didn’t just police trade, it was one of the 4 official departments of the Royal army. A committee of 5 members was appointed to coordinate with the Admiral of the fleet, indicating numerous war ships. Pirate ships (Himsrīkā) were pursued & destroyed by the Navy
Naval Warfare in ancient India, The Indian Historical Quarterly, Vol.4, No.4 1930 – Prithwis Chandra Chakravarti
Kautilya’s Arthashastra (English Translation) – R. Shamasatry