Much larger attack forces are currently cruising the Atlantic and Pacific oceans, and have been doing so for decades. The oceans are international waters, giant voids where it's hard to know where your enemy is.
They can be a thousand miles away from your coast and launch cruise missiles with more fire power than that of Pearl Harbour. If there is a radar/signal disturbance on your coast which can help them, they will take advantage of it.
https://en.wikipedia.org/wiki/R%27lyeh