Although it's true that you can access the island via the ferry service, and subsequently pay several dollars for parking and entry at Honeymoon Island State Park (not Caledesi) and then pay for the ferry ride to Caledisi, there is a free option, other than boating in, that many people know nothing about. If you don't mind a little exercise then you can choose to park on the North end of Clearwater beach and hike the 2 miles onto the island. This is, honestly, one of the most beautiful beach hikes that I have ever been on. Once on the island you can search for trail markers along the dunes and find where the Caledisi nature trail ends (or begins on this journey).
Pros: Natural Features, Trails, trails, etc., Snack bar!!
Cons: , go when cool