dear student

Take up science stream including maths in +2. Study well during these years. After completing, do your own research about where you want to pursue your marine engg. There are various colleges under IMU(Indian Maritime University) head office in Chennai. This university gives us the final degree of B.tech in Marine Engineering. But you can study in any of the colleges under IMU. Look for the college which you think will be good for you.

You will need to appear entrance tests,personal interviews,  nd medicals to get entry into the colleges

hope it helps

All the best!!!