Nah! Terrorists have guns. They use them. The searider wouldn't stand a chance of getting near enough to deploy the thing as shown. Be good for the maritime equivalent of Police Interceptors though - waterborne stinger.
I remember a long time ago, while moored on a buoy in a harbour (before marinas) a speedboat kept charging through the moorings every ten minutes or so. He took the same route each time, very close to several occupied boats. By mid afternoon we were all fed up.
. An enterprising chap went for a row in his dinghy, for exercise
. Next time the speedboat passed through its engine stopped with a bang. Seems it caught a floating rope in the prop.
There was no one in the cockpits of any of the occupied boats. No one saw anything.
I think he eventually drifted alongside a wall - but of course, I wasn't watching.