Not necessarily wrong. Impractical would be a better description. Initially the fire was 2 or 3 decks below the open upper deck. So there was very little to any heat transfer to that top deck for the first day or so. Once the fire started spreading upwards and the heat became an issue, would multiple Bambi water drops help. As a last resort yes. It's better then nothing. The problem becomes sustaining it. They would have to sustain a drop every say 30 seconds 24 hours a day for several days to be effective. The other part of the problem is that dropping 1600 to 4000 pounds of water from even a low height, things are going to move and break. So you couldn't even fight the fire inside, or come and go while doing that.What I was thinking was using a helicopter drop over a concentrated area and not spread out like in a forest fire. Obviously I guess I was wrong.
They did it for the Bon Homme Richard fire a few years ago, but it was more public relations then anything else. From the onset the ship was doomed and a lot mutual aid departments left the scene early.
If the fire was contained to the open top deck, with multiple cars burning, yeah it would be pretty effective. I've seen water bombers in rural areas drop on burning cars and trucks.
Basically in a ship board fire, from the limited knowledge I have, is that you have a fire start in say a cabin. That fire if unchecked can grow fowards, backwards, left, right, up and down. Where in a typical fire, it goes up left and right. The steel or metal, that the cabin is surrounded by will transfer heat everywhere. And it can't be vented like a multil story building. So the decks themselves will radiate heat to the surrounding areas until something there reaches its ignition point. At least in a multi story bldg you can vent heat and smoke and somewhat confine a fire. Not so much on a ship. Which is why they try cooling the surrounding areas with copius amounts of water.