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

Arrest drug smugglers, rescue stranded civilians, etc. they combine a maritime police and emergency service as well as an armed response unit.