Saint Marys Entrance is a sound at the mouth of the Saint Marys River, forming a tidal inlet that connects the Cumberland Sound and the Intracoastal Waterway to the Atlantic Ocean. It is located on the border of Camden County, Georgia, and Nassau County, Florida. This is a coastal marine environment where paddling conditions are dominated by tides, winds, and significant commercial and recreational boat traffic. The entrance channel is being narrow, with exposed riprap lining one side. A public boat launch ramp is situated on the port side when entering from the sea, providing a primary access point for paddlers. This area is exposed to open ocean conditions, meaning paddlers must be prepared for potential surf at the ocean entrance, significant wind fetch across the water, and strong tidal currents that flow through the constricted inlet. The timing of tides is critical; planning to paddle with the tidal flow is advisable, and crossing the marked navigation channel requires extreme caution due to vessel traffic. The surrounding landscape features numerous estuarine creeks, cuts, and islands, such as Little Cumberland Island, offering a maze of protected waterways to explore once away from the main inlet. The area is part of a broader network of marshes and sounds, with bluffs like Brickhill Bluff marking the shoreline. Water temperatures will follow seasonal patterns for the southeastern Atlantic coast, being warm in summer and mild in winter. Paddlers should be aware of ongoing maritime operations, such as dredging and material disposal activities south of the entrance, which may create temporary hazards or restricted zones.