Shells aren't the only thing that make-up limestones- skeletal fragments from coral and forams, among other things.

Shells aren't the only thing that make-up limestones- skeletal fragments from coral and forams, among other things. However these all consist of calcium carbonate (CaCO3), which reacts and is soluble to even weak acids. Given that rainwater is slightly acidic, use this information to explain why Florida, which primarily consists of limestone bedrock, has so many sink-holes.