Florida is a fossil hunter’s paradise. You don’t need a pick and shovel, just a good eye. Unlike the fossils of the American Northwest, few Florida fossils are encased in rock. They are more likely to be found lying loose on the beach or among the gravel of a small stream. You can hunt for fossils by yourself, or take a professionally guided trip.  If you intend to hunt for fossils by yourself, you will need a permit , which cost $5.00. However you don’t need a permit if you want to collect fossilized sharks teeth, shells or plants.

The fossilized remains of large mammals such as saber-toothed cats, giant ground sloths, and cave bears are abundant in Florida’s caves, sinkholes and rivers. Page through the 1958 publication Fossil Mammals of Florida (pdf), you will be amazed at the variety of mammals that were walking around in Florida just 100,000 years ago.

In the 1950’s and 1960’s it used to be quite common to come across a 2-kg (4.4lb) tooth of an ice age mammoth in the Ichnetucknee or Withlacoochee River. You are much less likely to be that lucky today but one can still find smaller teeth, bones and the occasional whale vertebrae in these and other waterways.

Fossil seashells are common on the banks of rivers, and much of the state’s limestone bedrock is made up of the shells of animals that lived in the shallow seas that once covered Florida. Different types of limestone are found in different parts of the state. Limestone in the Florida Keys consists mainly of fossilized corals. Along the east coast, early Floridians quarried great quantities of a limestone rock called ‘coquina.’ The Castillo de San Marcos in St Augustine is built entirely of coquina, and if you look closely at the walls of this fort you can see millions of fossilized sharks teeth. A few miles further south, the beach at Washington Gardens is covered with coquina rocks.

Fossil shark teeth are also fairly easy to find in streams and rivers, and enormous numbers of them turn up on the beaches of southwestern Florida. Part of the reason these teeth are so abundant is that sharks shed and replace tens of thousands of teeth in their lifetime – one shark might produce and loose 20,000 teeth in 30 years. Look for them in rivers and creeks especially after a heavy rain. The rainwater carves new deposits from the banks and deposits the fossils on gravel bars and shallow pebbly areas on the creek bed. Look for something dark and shiny, especially in places where the creek bends.
If you are really lucky you might find a 6-inch tooth from a 60 foot-long Megalodon shark. Megalodon sharks disappeared about 2 million years ago, but their huge fossil teeth are still found in Florida, in the streams and rivers around Gainesville and along the Peace River and its tributaries.

Source: Wild Florida ecotravel guide