This is a Whale Shark. It is harmless to humans unless you get in its way: which I did and got a tail swipe upside the head for my mistake. This photo was taken in 2006 in the Gulf of Mexico, just north of the island of Holbox, Mexico. Due to the currents, there are dense nutrients in the water there, and Whale Sharks come in the hundreds to feed. While we were there we saw 60-70 at a time on the first day. On the second day, we only saw this one, but we were able to stay with it for a couple of hours. The Mexican government has strict rules regarding the Whale Sharks which only allows snorkeling and prohibits the use of sunscreen because of the chemicals. Some in our group (who shall remain nameless but you know who you are) were yelled at while we were still at the dock for putting on sunscreen. They are very strict about it.