I've only been out to the Fort on a charter trip, but you may have better luck down in the Florida Conch Divers forum,,I pulled this of the NPS site:
Private boaters have a prime opportunity to visit the fort. Nautical charts for the route can be purchased at marinas and boating supply outlets in Key West. Information can be obtained in Key West from the U.S. Coast Guard station, the Chamber of Commerce, and the Charter Boat Association. Boaters should be aware of the possibility of extreme rough seas.
If you visit using your personal boat, please bring at least two anchors and NOAA chart 11438. Overnight anchoring is limited to within one mile of Garden Key; there are no overnight anchoring buoys. Dockage at Garden Key is limited to two hours daily, sunrise to sunset.
Docking facilities are provided for park visitors and park operations. Load, unload, and moor vessels only where designated on the public dock. Moor private vessels no more than 2 hours between sunrise and sundown; overnight mooring to docks or piers is prohibited. The park superientendent may waive these regulations in emergencies that threaten life or property.
Seaplane approaches, landings, and takeoffs are limited to within 1 mile of the fort. Moor seaplanes only in the designated area at Garden Key.
Dumping or throwing overboard bottles, cans, paper, or other trash on park grounds or in the water is prohibited. It is illegal to pump holding tanks into park waters. Warning: Park waters over shallow coral heads and reefs are protected and may cause severe damage to boats and equipment if stuck. Use caution in all park areas.
