CBSE 12th

Hi Prakash,
To take admission in Merchant Navy, you need to pass 12th in Science (Physics, Chemistry, Maths) with 1 year pre-sea training as a deck cadet.
You can also join it directly after B.Tech in marine engineering, mechanical, electrical, electronics & telecommunication, naval architect.
If you pursue B.Sc (Nautical Science) in the officer cadre, it will lead you to become captain after 5-7 years of experience.
Except marine engineering candidates, others have to undergo a 10 months pre-sea training which is offered by many institute and port trusts or recruiting company itself. After that you will be appointed as a 5th or junior engineer. It will take 5-7 years depending on your abilities to become a'chief engineer'.
Ample scope is available in this field. 'Merchant Navy is the backbone of international trade, carrying cargo across the globe'. Prospects and career growth will depend on your skills, qualification and performance.

Rahul, in the current scenario both are equally beneficial. The new notification of Ministry of HRD demands 75% in 12th.
Another thing is that if your JEE rank is not very good or doesn't let you have admission in a good college, you can go for good private universities like Lovely Professional University, Jaypee University, BML Munjal University, etc.
Most of the private universities offer admission on
1. Basis of marks in class 12
2. JEE marks
3. Their own tests
These universities are no less than govt.universities these days. They are a hub of quality education and good placements.
Some even offer good scholarships on above mentioned three criteria.
Check their websites for more details.
Good Luck.