Egmont Key, just outside Tampa Bay, is a great place for a day visit and an overnight as well if you can tolerate some roll. The key is a state park with excellent beaches, clear water, and extensive walking trails. The wildlife is impressive.
The southern end of Egmont Key is a wildlife refuge with limited ability to go ashore. If you look closely at the map above, however, you will note that there is a small strip along the shoreline of the northeast refuge area where it is OK to visit the beach. The main anchorage is also off that beach. We anchored there in a south wind. There was some protection afforded by the southern extent of the island as it curves eastward, but it was not enough to eliminate all swells.
The beaches are glorious all around the island, and the trails thick with native palms make for a pleasant walk. We found the fishing good as well.