
Dear Nuno,
I think you didn't pay enough attention to what you read.
Read: INSV Kaundinya is an Indian navy sailing vessels built using ship-to-ship techniques. Its design is BASED on a 5th-century CE merchant ship DEPICTED IN THE MURALS OF CAVE 17 OF AJANTA CAVES COMPLEX.
The detail is here: DEPICTED IN THE MURALS OF CAVE 17 OF AJANTA CAVES COMPLEX.
The ship DEPICTED IN THE MURALS is a representation of what had already been built in previous centuries, including those of the 5th century CE.
INDUS VALLEY CIVILIZATION (3000-1500 BC): A sophisticated maritime network emerged, with ports such as Lothal (in India), which maintained direct trade with Mesopotamia and the Persian Gulf, USING BOATS TO TRANSPORT GOODS across the Arabian Sea.
Socotra (Yemen) and ports in Oman and the Persian Gulf were vital stops, with direct routes to India also established from Yemen.
Conclusion: Boats were being built for commercial purposes AS EARLY AS 3000 BC.
Have you read William Dalrymple's book, titled The Golden Road?
I visited Ajanta and Ellora twice from Aurangabad.
Regards.