Yes, that would certainly seem to be a pretty obvious arrow. Though at 100 miles out, you do have some time to run (certainly more time to run when launching at 10 miles and unless I understand poorly, that usually gives you away as well).
From the article it says you have to start with a large velocity, so the option of a quiet launch and then run before it gets up to ludicrous speed isn’t there.
It would have to travel at almost 4000 mph. Quite a feat underwater.