Jake that is a large difference in elevation between hi and low tide for a floating dock. Do they even use floating docks up there? We have a very large (60 mile long) lake close to where I live. They raise and lower the lake level in the winter for water for the hydroelectric dam. The difference is about the same 3 feet. The docks sit on encapsulated foam blocks with cables holding them in place with the shoreline. The walkway running down to the dock is hinged at both ends to pivot with the rise and fall of the lake level.
