I suppose if it were up to me, I'd start by interdicting the lead boats and/or "flagship" boats one or two at a time, as far out as possible. I'd follow up by parking a few corvettes at the twelve-mile line, fire some warning shots, and make it abundantly clear that any vessel that continued to approach would indeed be sunk. And I'd finish by providing world-class maritime search and rescue services to the survivors of whichever boats turned out to be crewed by retarded confrontation junkies with an invincibility complex.