Countermeasures
anything that can deflect the beam
anything that can diffuse the beam
anything that can overwhelm the targeting
anything that can make the laser overheat
location - on the sea
targets - other ships, boats, aircraft
sending a flood of small drones at it, loaded with marbles and smoke bombs should work a treat. then, once the air inbetween has been "tainted" with airborne glass globules and smoke, you send in even more, and if everything goes to plan, the laser overheats trying to penetrate the airborne mist it has itself created.