Is Metal Detecting allowed in Florida state parks: YES, many public beaches between high tide line and the toe of the dune.
Each park in Florida seems to have its own ‘Management Procedures for Archaeological and Historical Sites and Properties on State — Owned or controlled lands’ document. The all have the same sections with slightly different verbiage. However I found that they all say the same thing on Metal Detecting. Link to one of them is HERE
B. Archeological Sites
9. Excavation and collection of archaeological and historic sites on state lands without a permit from the Division are a violation of state law and shall be reported to a low enforcement officer. The use of metal detectors to search for historic artifacts shall be prohibited on state lands except when authorized in a 1A-32, F.A.C research permit from the Division.
I also found this on FAQ section of the Florida Department of State Division of Historical Resources website. Link is HERE:
Q: Is metal detecting prohibited on state property?
A: Metal detecting on State land is generally prohibited with few exceptions. Many public beaches allow metal detecting between the high tide line and the toe of the dune. Beaches that are part of State and Federal Parks, Preserves, Sanctuaries and military installations will have specific rules governing metal detecting; always consult with the park, or property manager.
FMDAC Disclaimer: FMDAC assumes no responsibility for any person who knowingly or accidentally violates any state park regulation. Although FMDAC will try to keep this information current we cannot anticipate how each regulation will be interpreted by a specific park department, park employee or other government employee. It is the sole responsibility of each individual to know and obey the regulations of the park or area they are visiting and or metal detecting.