Didn't see much of an effort to extinguish the fire. Great video job.

#1 if the fire is inside a metal compartiment(like the hull of this boat) it is saver to let it burn, like a oven. if they add water or foam, it can break and spread burning fuel all over the place. It looks like they keep the concrete wet.

#1 There are stages of a fire where it's deemed fit to try to put it out or not. In this case, it was way beyond any saving, so the best thing is to let it burn out under controlled circumstances. Those 3 trucks wouldn't have enough water to put that fire out anyway. At that heat, the water just vapors and loses almost all of it's cooling properties. These fires are a lot hotter than a normal wood fire, due to all the chemicals that are burning, so normal methods won't work too well, unless you had just put the entire boat into the ocean.

#3 They probably did decide to just let it burn itself out,not worth saving, but fire trucks have the capability for unlimited water supply
by pumping water out of any available water source by just dropping a suction hose down
into the water.

That's what I call expensive fire

I guess if the rotors start melting you know you're too close.

What would happen if the would have used a firefighting airplane?
Maybe better first throwing the boat into the sea and then the firefighter plane. I hope that it is insured.