One of these not so feasible theories is the stork theory. According to Peter Piermarini, a graduate student in the University of Florida's zoology department, a man by the name of Grady had seen birds flying around with stingray in their beaks. The type of bird was not mentioned. This man had supposedly seen baby stingray, better known as pups, fall from the sky into the river. The actual phenomenon of pups falling out of pregnant female rays is actually quite common.
Stingray give birth to fully developed, live young.
This is very unlike that of skates, which lay egg cases. When the female stingray are near full term, even the slightest stress can cause them to release their young. So, Grady hypothesized that the stingray invasion of freshwater was initiated by a bird with a pregnant stingray in its beak. Obviously, this theory is not well accepted among the scientific community. Another theory, as well as the most accepted, is based on the geological history of the St. Johns River and the salinity tolerance of the Atlantic stingray.