Mystery Monday revealed! The answer is:
Meet the largest fish on the planet, none other than the whale shark, Rhynchodon typus. While this behemoth is about 30 feet long at sexual maturity, a very large individual can get upwards of 60 feet. And they are thought to be long lived as well, reaching 80 years of age or more. In the Bay of La Paz where they are seen on Searcher trips when the weather cooperates (and most of the time it does), there are aggregations of juveniles. Interestingly, most of these sharks are males. The shallow waters are a great place to see them up close, though we have spotted them in deeper oceanic waters also. The juveniles are feeding on clouds of plankton known as copepods, which the remoras that hitch a ride on the whale sharks also feed on. Researchers have also found that some juvenile whale sharks migrate in the Gulf of California between Bahia de La Paz and Bahia de los Ángeles after spending a month or more in the shallow bays.”~Paul Jones
