Imagine yourself visiting the Everglades 10,000 years ago, but instead of standing, you're on a boat and the only land you can see is in the distance. In fact, you would probably be quite disappointed because the Everglades don't even exist yet.
The Earth's climate is always fluctuating between glacial cycles that both alter the terrain and influence sea level over thousands of years1. Florida's land mass developed during times of high sea level, when deep oceans covered the peninsula and deposited sediments and sand onto an existing mantle of ancient limestone1. Periodically, this growing land mass emerged from the ocean floor as alternating periods of glaciation transferred more of the planet's water to ice on land and sea level declined considerably.