I don't agree at all... the airboat might be the perfect rescue boat. If you're worried about noise, and outboard motor makes noise too. But for pulling people off of rooftops or quickly transiting shallow floods, an airboat can't be beat.
I'd get as many of them as I could.
Along those lines, LCACs would be ideal for transporting stuff into the city - especially since most of the roads and bridges are either underwater or just plain *gone*.
TXCN is reporting that local Wal-Marts are donating food, water, and televisions (among other things) to evac shelters, no prompting needed and no questions asked.