Dry Tortugas National Park

Dry Tortugas National Park preserves Fort Jefferson and the Dry Tortugas section of the Florida Keys. The park covers 101 mi² (262 km²), mostly water, about 68 statute miles (109 km) west of Key West in the Gulf of Mexico.
It is famous for abundant sea life, colorful coral reefs and legends of shipwrecks and sunken treasures. The park's centerpiece is Fort Jefferson, a massive but unfinished coastal fortress. It is the largest masonry structure in the Western Hemisphere,[1][2] and is composed of over 16 million bricks. The park plays host to almost 80,000 visitors each year. The park is accessible only by seaplane or boat. Activities include snorkeling, picnicking, scuba diving, saltwater fishing and birdwatching. (from: wikipedia)

Biscayne National Park

The park protects four primary ecosystems. Along the mainland shoreline of Biscayne Bay lies the longest stretch of Mangrove Forest on Florida's east coast. Though only a small part of the park, mangroves are critically important to the park's food chain. Biscayne Bay, the park's namesake, is a broad, shallow body of water teeming with life. Its southern end, still relatively pristine, provides abundant recreational opportunities. The Florida Keys are ancient coral reefs left exposed when sea levels dropped (for more information on the park's geology, see Geology Fieldnotes — Biscayne). The northernmost 50 or so islands, untethered by roads or bridges, offer a glimpse into what all of the Keys looked like before development. The world's third-longest Coral Reef tract begins in Biscayne National Park. Home to over 200 species of fish and countless other marine plants and animals, it is one of the best-preserved reefs in Florida. (from: http://www.nps.gov/archive/bisc/resource/index.htm)

Everglades National Park

Everglades National Park is the largest subtropical wilderness in the United States. The area boasts rare and endangered species, such as the American crocodile, Florida panther, and West Indian manatee. It has been designated an International Biosphere Reserve, a World Heritage Site, and a Wetland of International Importance, in recognition of its significance to all the people of the world.