The process of fossilization starts when the shark sheds its teeth and they sink to the ocean floor, where they're covered by sediment and protected from damage. Sharks shed their teeth and replace them with new teeth constantly through their lifetimes, and a single shark may shed thousands of teeth during its life. The Florida Museum of Natural History explains that shark teeth are preserved through permineralization, in which water deposits minerals such as silica and calcite into the tooth's open pores. These deposited minerals cause the varying colors of shark teeth fossils found in Florida.
The shark tooth fossils found in Florida today were shed back when much of what is now Florida was under a shallow sea. They may be found in sedimentary rocks or unconsolidated sediments. Parts of Florida have been under water and above the ocean level a number of times over geologic time as climate change has raised and lowered ocean levels. Some fossil shark teeth may have been buried, then exposed to erosion, then reburied over time, while others may be undisturbed in the sediments where they were buried hundreds of thousands or millions of years ago. The processes continue today.
The slowly evolving shark predates humans by hundreds of millions of years, populating the world's oceans long before animals walked on land. The age of sediments can often be identified by the presence of teeth of specific shark species, but identifying the sharks can be problematic. The teeth are rarely found together, and the tremendous differences in sharks' teeth between the sexes, through a shark's lifetime, and even within one shark's mouth make it tough even for the expert to make identifications.
Florida's bedrock is littered with the fossil record of the ocean's rises and falls through time, but that doesn't mean you can turn over any rock and come up with shark's tooth fossils. Your best bets are shallow marine environments such as Venice Beach, or places that used to be shallow marine environments. Sharks would have been there thousands or millions of years ago, looking for food and shelter -- and shedding teeth.
