Underwater caves in Florida are primarily formed due to the abundance of limestone layers just situated below the ground, forming the "Floridan Aquifer." Layers of these limestones are believed to be thousands of meters thick. When rainwater is being seeped into the ground, it softens the calcite present in limestones due to its acidic nature until it is dissolved. This leads to the formation of cavities and tunnels which eventually becomes an interconnected network of passages over time. As water continues flowing through these passages, which builds up from the bottom of these cavernous empty spaces, underwater caves are then formed. Therefore, the first choice is the answer.
