I believe Iran, when they say they are mass producing a missile that can be connected to a small speed boat. I believe them when they say these missiles are capable of doing damage to an American navy ship, as minor as that damage might be in reality.
But I don’t believe that Iran’s missile are particularly advanced. It would surprise me if those missiles could sink anything greater small holes in the bigger boats.
I think the main concern for the navy might be remote controlled boats filled with explosives. That could be troublesome.
Iran has been exporting advanced Chinese anti-ship missiles for years. What makes you think they couldn’t copy them?
http://en.wikipedia.org/wiki/INS_Hanit