The Florida Fish and Wildlife Service (FWS) has announced new restriction on access to the Three Sisters Springs. Manatees (Trichechus manatus latirostris) visit the springs during cold weather periods. New studies have shown that when Gulf water temperatures at Shell Island dropped to below 17°C, this increased manatee numbers in the Spring. Hence the FWS will close the Spring to visitors when water temperatures at Shell Island drop below 17°C and only reopen when it rises above that temperature for 24 hours or longer.
Real time water temperatures at Shell Island are available here. If planning to visit the Spring, it may be worth consulting with the FWS to ensure that it will be open.