what i should chose for mtech Naval Architecture and ocean engineering in iit Kharagpur or Ocean engineering in iit Madras? 

Hi there,
A degree in naval architecture or marine engineering prepares professionals for two different but related careers in the realm of designing ships and the systems that allow ships to run. Either degree would allow a person to work in the Navy or in the private sector, or positions could entail supervising other workers and using computer design software.
Scopes
After completing your naval architecture course, you can join Indian navy, coast guard as an officer.
Placements at IIT madras
Naval Architecture & Ocean Engineering- Rs. 4.4 lakhs to Rs. 20 lakhs per annum
Highest Package Offered (International)
$129,500 per annum
Highest Package Offered (Domestic)
Rs 30 lakh per annum
Hope this helps
All the best.