I love the Navy we do many things but the main strategic task of the navy also may incorporate nuclear deterrence by use of submarine-launched ballistic missiles and other field of work. 
I don't know much about the Navy. My best friend's husband used to serve in the Navy though.
I respect all Navy vets, The main role of the Navy is the projection of force into areas beyond a country's shores take for example, to protect sea-lanes, ferry troops, or attack other navies, ports, or shore installations.