Lagoon - A body of water separated from the sea by a seciton of land, such as a barrier island. Not to be confused with an Estuary.
Longshore Current - When waves strike a shore at an angle, and then retreat from the beach at an angle, the back and forth motion creates a sort of “zigzag” pattern. This results in a current that runs along (parallel to) the beach. This is the current that takes you down the beach when you are floating in the water.
Longshore Drift - The movement of sand caused by longshore current. This movement will cause inlets to close up, as did the inlet that once was located at the site of the Thousand Islands. Jetties are used to prevent this movement of sand into the inlet channel, but they also starve beaches of the natural source of sand. Some people believe that a form of dredge and fill referred to somewhat errantly as “beach re-nourishment” is a viable solution to the beach erosion.