This one?
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http://www.hoax-slayer.com/new-orleans-crocodile.html '
Commentary:
The photographs that arrive with this email forward supposedly depict a giant man-eating crocodile caught swimming the flooded streets of New Orleans in the wake of destruction caused by 2005's Hurricane Katrina. The photographs are real. However, they were not taken in New Orleans. The images were displayed on various websites such as markhope.com and began circulating around the Internet via email and online forum posts long before Hurricane Katrina struck.
Apparently, the photographs were actually taken in Pointe Noire, Republic of the Congo, during 2003. The original email message is very similar to the current version, except that the prankster has relocated the action to New Orleans rather than Africa. According to an article discussing the original message on About.com, information about this giant crocodile was published on July 17, 2003 in La Semaine Africaine, a French language Congolese magazine.
Also, it appears that the length, weight and age of the reptile are exaggerated in both the original Pointe Noire version of the email and the 2005 New Orleans mutation.
The About.com article notes that the magazine story records the crocodile as measuring 5 meters (around 16 feet) and weighing 850 kilos around (1,874 lbs). The animal's age is estimated to be around 50 years rather than 80 years as claimed in the messages.
The animal depicted is a Nile crocodile. Nile crocodiles are found across a large portion of Africa (but certainly not the New Orleans region) and do indeed grow to enormous sizes. According to an article on the Crocodilian Species website, Crocodylus niloticus has an average adult length of around 5 meters (about 16 feet) and has been reported as reaching 6 meters (around 19 feet) in rare cases. The article notes: