Here is more evidence that laser weapons are on the way, although the video does not look that impressive. We have already seen video of lasers taking out air targets, which has to be more demanding, so the fact that lasers can start a fire on a boat should not be surprising.
What caught my attention was this statement, “Lasers can address a number of emerging threats, enabling the fleet to maintain freedom of operation, yet with a very low cost of operation. Lasers will offset the use of higher cost kinetic defenses for a number of these threats, substantially reducing the total cost of ship defense.” –Lasers are the low cost option?

The press release says that the system, “tracked and damaged moving, remotely piloted, unmanned small boats traveling at representative speeds and ranges.” In the video the boat’s engines appear to be idling, there is no attempt at evasion, and the range is not stated. Also the clip does not appear to be continuous, so the time required is not clear. Even apparently edited, it takes some time before the fire breaks out. Presumably the fire was only as large as it was because the engines were running, bringing gasoline to the fire.
Still, I can see some circumstances where a weapon that can be turned down to less than lethal settings, and be applied very precisely, might be useful.
Lasers do seem to have a future within the lifetime of the ships the Coast Guard is planning now. Perhaps it would be prudent to make sure that they have the electrical generating capacity to use these weapons. This seems another reason to look closely at diesel electric or at least hybrid propulsion for the Offshore Patrol Cutters. As the captain of the Starship Enterprise might say, the command may be, “Divert power to the shields.”
In a real world situation, the crew of an attacking boat would be blind long before the fire starts.
Sort of related, there is this news release about a laser intended to “visually disrupt” without causing permanent damage: http://eon.businesswire.com/news/eon/20110413005767/en/laser/maritime/green-laser
There is also the potential for the the attacking boat to be remotely controlled, which might make the blinding option ineffective.
There is a laser weapon actually being deployed: http://news.usni.org/2013/04/08/navy-to-deploy-anti-uav-small-boat-laser-next-year-to-gulf
More evidence that the laser may become a viable weapon, even in a relatively small size:
http://www.lockheedmartin.com/us/news/press-releases/2013/may/0507-ss-adam.html
The Navy is starting to deploy lasers in several sizes. https://news.usni.org/2019/05/30/navy-to-field-high-energy-laser-weapon-laser-dazzler-on-ships-this-year-as-development-continues#more-65959