Ruins of Fort Dade from the Spanish-American War, the Egmont Key Lighthouse, wildlife, well-kept trails, beautiful beaches, and snorkeling.
Egmont Key Sate Park is only accessibly by boat, so be sure to book ahead if you need a ride. Several tour companies offer relatively cheap rides to and from the island, paired with snorkeling excursions at the ruins on the west side of the island.
The island ferry departs from Fort De Soto State Park, which is easily accessible and offers admission for only $5 per car. To make the most of your day on the island, be sure to visit the lighthouse (built in 1858), the ruins of Fort Dade, and enjoy the abundance of wildlife. Fort Dade was constructed during the Spanish-American War in the early 1900s, and the remains of the town, fort, and beautiful brick streets are still well intact.
Today, the abandoned town has been taken over by the island's tortoise population; you can expect to see them wandering fearlessly through the old structures. Also, keep an eye out for bottle nose dolphins, manatees, and the variety of birds at the bird sanctuary on the south end of the island.