I’m no expert, but I assume there’s a reason why ALL navies have CIWS for last-ditch air defense and other stabilized gun systems (12.7mm to 30-35mm) for taking on speedboats and similar threats.
A CIWS has a high rate of fire, but does it have a stabilization mechanism to shoot up a boat bouncing around in the water? It’s easier to create a wall of lead to stop an incoming missile than to take a few shots at a speed boat unless its sitting still. Experienced navy folks will be able to explain better.
Might be harder for the CWIS guidance to pick up the boat against the ocean surface.