Alligator Reef Sanctuary Preservation Area

Alligator Reef Sanctuary Preservation Area (SPA) is known world-wide for its diverse variety of marine life. In a pioneering, 1968 survey of coral reef fish diversity, researchers documented 516 species from Alligator Reef. A half-century later, the list was updated with numerous name changes and revisions, adding 102 additional species to the list. Additional surveys since then have added even more species to the list, bringing the total to 632 known species as of 2020. Known by an iconic black and white lighthouse that is visible from land in the Upper Keys, Alligator Reef lies just four and a half miles east of Indian Key, marking a habitat that bridges the shallow reefs of the Upper Keys and the deeper reefs of the Middle Keys.

A mostly white lighthouse surrounded by turquoise water with a few boats anchored nearby — Alligator Reef Lighthouse is the most readily visible lighthouse from the Overseas Highway in the Florida Keys. Photo: Jack Fishman

This rectangular SPA, just 0.32 square miles in size, is a small bank reef protecting a spur-and-groove system, reef crest, and a portion of the northeast rubble ridge. Tourists venture to the reef daily to relax in the serenity the reef provides. Many local dive and snorkel boats venture here to provide guided instruction, where the reef is ideal for beginning snorkelers and divers; some parts of the reef lie at a depth of only 8 feet.

Very high water temperatures in the summer of 2023 have caused widespread coral bleaching and mortality in the Florida Keys. Descriptions of coral cover or coral health on this page may not be accurate based on current conditions.

Special regulations apply here. Learn more about what activities are allowed in this type of zone.

A summary of all sanctuary regulations is available online. For the full text of sanctuary regulations, see 15 CFR 922 Subpart P.