Mechanical Engineering

You may refer to following link for list of top B.Tech Mechanical Engineering colleges in India: https://www.shiksha.com/b-tech/ranking/top-mechanical-engineering-colleges-in-india/48-2-0-0-0
There are multiple options to join Indian Navy after B.Tech Mechanical Engineer:
(a) CDS Entry: CDS entry consists of written exam conducted by the UPSC, followed by conduct of the SSB interview, medical test by Indian Navy (naval candidates only) and final preparation of merit list by UPSC. The appointment letter is issued by IHQ MoD/DMPR. The training of officers selected through this entry commences in the month of Jan/Jul and the advertisement is published in Nov/Jul.
(b) NCC Entry: The vacancies for Naval Wing Senior Div NCC C certificate holders are published along with CDSE advertisement. No written test is conducted for this entry. The eligible candidates are required to forward their application directly to IHQ MoD (N)/ DMPR through DGNCC. The candidates are deputed for SSB interview. After qualifying SSB these candidates undergo medical examination and if found fit, are inducted in the Indian Navy on the basis of All India Merit. The training of officers selected through this entry normally commences in the month of Jan/Jul every year.
(c) Direct Entry: The Direct entries are controlled by IHQ MoD (Navy) /DMPR and cater for both Permanent Commission (PC) and Short Service Commission (SSC). Advertisements calling for application from eligible candidates for such entries are published in the leading newspapers and Employment News twice in a year between Feb to May and Aug to Nov. The applications are received and candidates are shortlisted for SSB based on cut off decided by IHQ MoD (Navy)/ DMPR. The SSB qualified candidates undergo medical examination and if found fit, are inducted in the Indian Navy on the basis of All India Merit.

Hi,
It's great to see that you have discovered what you wish to do. My suggestion would be to analyze your skills in each of the field. By your question I assume that you are still in high school, in that case you might not be able to analyze yourself with respect to mechanical field. So start by analyzing yourself with respect to computer science like how well are you at programming (C, C+) and what's your proficiency in various computer applications like MS Office (Word, Power Point, Excel, Access, etc.), Media editing (audio &/or video), modeling and animation, etc. If you are good at it then you should go for it.
Being a mechanical engineer let me tell you that mechanical is a very vast field, in fact it is a combination of all the fields be it computer science, automobile, thermal (heat transfer, refrigeration and air conditioning, thermodynamics), chemical, physics, environment, supply chain management, etc. In order to test yourself with respect to mechanical make sure you are good at thermodynamics (basics are introduced in chemistry), mechanics (moment of inertia, newton's laws of motion, centroid, stress, strain, etc.), mathematics (especially differentiation and integration). These are some basic topics that are introduced at school level, which later in graduation and post-graduation gets elaborated.
PS: in high schools people generally have misconception that the mechanical field means just designing of automobiles and all. In reality mechanical is much more than that. In my opinion none of the fields can survive without mechanical field's support.