Hi there,
The blow picture is the answer to your question.

But before I explain it in little details, I just wish to know, if there is a profile other than engineering that you are looking out for, when it comes to be a part of the Navy Industry.

Since Merchant navy involves being on the sea, and transporting of commercial goods and people from one place to another, mostly by Sea, they too need the help of radars to communicate with their team on land.
Though they have the magnetic needle that gives them the directions, but still they need to co-ordinate with the team at the shore to get other information.

Here their means of communication is the radar, or the virtual means of communication.

If you notice, the above mentioned issues relate to what you guys are into.
A part of communicating using the virtual medium.
A electronics and communication engineer are the ones who study the internal devices of such modes of communication.

So if you are the ones who are into manufacturing the devices, who else can help to troubleshoot and help the Captain during the voyage.

Please note that in this industry, there are groups of engineers who work together as a team like the Mechanical engineer, Marine engineer and the telecom engineer.
Also the roles vary depending on the need at the particular time.

Also please note that your profile is divided into two aspects, i.e, in-house ground staffs, whereby you would be checking in when the ship is on the shore, so complete maintenance.
And also there are on board engineers, who accompany the aircrew team, so that if there are difficulty while flying they can be there to deal with the said difficulty.
But both the in-house and in-house team works in co-ordination.

Since the In-house team, is studying the machine in relation to other important factors like weather etc.

After completing your Graduation, you can join the Merchant Navy immediately as a Fourth engineer, whereby your job would be to take instructions and also get into doing the job.
As the time goes and you gain experience, there are internal exams you can clear, which helps you move up the ladder.

Remember, that since your job mainly deals with areas related to modes of communication, any industry right from Para-military to Aviation to Space is open for you.

Hope you get an insight from what is mentioned above.
In-case of further difficulty do write back.

Wish you all the very best..........

Know Your Right Engineering Branch - Take Engineering Branch Selector Test

@meghnamukherjee if you could speak more from perspective of merchant navy and defence. Your answer is more from electronics and communications students perspective

Edited the answer from the Merchant Navy perspective