Among the many rumors circulating in the aftermath of Hurricane Katrina is the claim that sharks have been seen prowling the flooded byways of New Orleans. "Sharks were reported swimming in the streets," declared an overseas newspaper account credited to AP and Reuters. "Sharks and alligators are eating people in downtown New Orleans," an unidentified rumormonger was overheard saying in Shreveport.
While I wouldn't want to chalk these reports up entirely to hysteria, I think we can safely say they're a tad exaggerated. Sifting through earlier news accounts in an effort to track the rumor back to its origin, I found repeated references to unnamed "authorities" and "officials" reporting one "3-foot shark cruising the city." Which authorities? Which officials? Digging further, I could only find mention of one by name: Mayor Aaron Broussard of Jefferson Parish (a New Orleans suburb), who, according to the Aug. 30 issue of the Palm Beach Post, "told residents Tuesday that at least one 3-foot shark had been spotted."
Again, that's one small shark reportedly sighted exactly where and by whom, we don't know and as far as we know he hadn't eaten anybody.
As for alligator sightings, those are to be expected in Louisiana waters under the best of circumstances, as are snake sightings, and even the occasional floating ant ball.

Comments
The floating ant balls I can believe were there in parts of New Orleans. The alligators were there too I would believe. I live 10 miles outside of New Orleans and have not seen many alligators in my life time though. It is a safe city except for its ghosts. Now the ghosts are a different story all together. They exists in New Orleans more then in any other city. Come down and take a tour.
Aaron Broussard was, at that time, the President of Jefferson Parish, Louisiana. A parish in Louisiana is like a county in other states. There was TV footage of an approx. 3-ft shark (probably a baby Bull shark) swimming in the flood waters around the Landmark Hotel in Metairie, Louisiana (Metairie is a suburb of New Orleans, and is in unincorporated Jefferson Parish). The shark was spotted by Jefferson Parish Sheriffs’ Deputies who were in a boat at the hotel to retrieve other Deputies who had stayed in the hotel during the storm. The shark likely swam out, or was pushed out, of Lake Pontchartrain by the storm surge. The Landmark Hotel is approx. 2 miles from Lake Pontchartrain. I have been unable to locate the news footage, but will post the link here if I find it.