What does the US Coast Guard do that the Navy and the Marines can’t do?

Question

I’m not from the US and have no military experience either. So the US has apparently 3 maritime branches in the uniformed services and the Coast Guard is, well guarding the coasts of the US. And the other branches can’t do that?

In: Other

Answer 1

Surf Narco Subs 

Also go into poverty whenever the annual defense spending bill slips and they only make protections for DoD.