The most sophisticated vessel in the US Navy was working alongside the USS Bataan immediately after Katrina hit:

...four MH-53 Sea Stallion and two HH-60 Seahawk helicopters from USS Bataan were flying medical-evacuation and search-and-rescue missions in Louisiana, and Bataan's hospital was preparing for possible use for medical support. Bataan, based out of Naval Station Ingleside, Texas, is in the waters off the Louisiana coast. High Speed Vessel Swift, also based at Ingleside, sailed to the waters off Louisiana to provide support, as well.

If that fool Michael Brown could get it deployed so quickly, what kind of fool is Paul Krugman for claiming the federal governement wasn't mobilizing its assets for disaster relief?