Our coastal lakes have been opening to the Gulf for many, many years.
The lakes fill with rain and streams and when the lake level reaches the point where the dunes cannot contain it any longer, it breaks through and empties into the Gulf.
The lake water is brown in color due to organic matter, is harmless and disappears soon after the outflow stops.
Seeing a lake break through, first as a trickle which widens quickly into a raging torrent, is an amazing thing to watch.