Is Key West, Florida, the southernmost point in the contiguous United States continuously above water?

Key West is billed as the Southernmost point in the Continental US. The wording is not accurate. Florida's official southernmost point is Ballast Key, a privately owned island south and west of Key West. Signs on that island strictly prohibit unauthorized visitors. The above pictured marker is not even the southernmost point of Key West Island. The private yard directly to the southeast of the buoy is obviously farther south. Land on the Truman Annex property just west-southwest of the buoy is the true southernmost point on the island, (approximately 900 feet (270 m) farther south), but it has no marker since it is U.S. Navy property and cannot be entered by civilian tourists. The southernmost part of Key West Island accessible to civilians is the beach area of Fort Zachary Taylor Historic State Park at approximately 24.545142 N, 81.80964 W, and approximately 500 feet (150 m) farther south than the marker.

The claim on the buoy stating "90 miles to Cuba" is a rounded number, since Cuba, at its closest point is 94 statute (81 nautical) miles due south.