Congrats on securing a great rank Kotana. Ocean engineering and naval marine engineering is a good branch if you are passionate about that particular field of study, but if you only want to opt that branch  just because of IIT Madras I would suggest the otherwise.

College is important, but branch is more important. 

I suggest you go for newer IITs and a better branch  as the new IITS too are catching up very fast in terms of facilities and placements. Rest lies in your hand. Best of luck