Ask about the weather conditions. Poor visibility, strong winds & surge from waves reduce safe interaction at the reef.
Remember that even the lightest touch with hands, fins or other dive and snorkel equipment can damage sensitive coral polyps, the small living animals that make up the hard and soft corals at the reef.
Snorkelers should wear buoyancy control or snorkel vests to allow gear adjustments without standing on the coral.
Avoid contact with the ocean bottom; properly weighted divers should practice proper buoyancy control. Sandy areas that appear barren may support new growth if left undisturbed.
Please don't feed the fish; it destroys their natural feeding habits, and avoids any potential injury to you or the marine life. Remember, it's illegal to harvest coral in Florida.
If you dive or snorkel on your own, be aware of reef mooring buoys to use instead of anchoring a boat; many dive and snorkel sites are located within the Florida Keys National Marine Sanctuary, and anchoring in these Sanctuary Preservation Areas (SPA) is prohibited.
(courtesy: Reef Relief, dedicated to the protection of coral reefs)