Docks on the Intracoastal and the Marshes

Bigger tides near the coast

The average gap between high and low tide is about 6 feet at Fernandina Beach, about 4.5 feet at Mayport and about 4.6 feet at St. Augustine Beach. A dock that works at high tide can leave the boat sitting in mud at low tide if it stops short.

That is why floating docks and boat lifts are common here. A floating section stays at the boat's level, and a lift keeps the hull clear whatever the tide does.

Crossing the marsh

Many lots on the Intracoastal and the tidal creeks have salt marsh between the yard and open water. The walkway crosses the marsh on pilings, high enough to let light reach the grass underneath, and the platform sits at the water's edge.

A long walkway uses much of the area allowed over the water, so plan the platform, the lift and any roof together.

Aquatic preserves

Large parts of the coastal marsh are state aquatic preserves: the Nassau River-St. Johns River Marshes and Fort Clinch preserves to the north, and the Guana River Marsh and Pellicer Creek preserves to the south. Docks in a preserve face tighter limits on size and design. Ask the builder to check your location first, because it changes what can be built.

Salt water

Salt water is hardest on metal. Bolts, brackets, lift cables and motors wear faster near the inlets than upriver. Ask what each metal part is made of and how it is serviced.

Which office issues the permit

Ponte Vedra Beach and St. Augustine addresses are in St. Johns County, Fernandina Beach is in Nassau County, and the beaches east of Jacksonville have their own city governments. The permits page covers the state and federal steps that apply everywhere.

Questions to ask

• How deep is the water at the end of the dock at low tide?
• Is my shoreline in an aquatic preserve?
• Fixed, floating or a mix for this tide range?
• How high does the walkway sit over the marsh?
• What metal parts are used, and how long do they last in salt water?