it is the water currents dragging in seaweed plants and other things.
Longshore Current..
longshore
"He walked along the beach."
it carries sand / sediment along the beach to another point often causing a spit or bar.
The prepositional phrase is "as you walked along the beach".
How sand and other materials are carried parallel to the shore by the waves. The waves approach the beach at an angle.Longshore drift is the movement of sediment along the coastline.Longshore drift is the transport of erosion sands along a shoreline by the current flowing along it.
Beach Drift
the process in which beach sediment move down a beach with the current
beach erosion is caused by the movement of ocean currents along the shoreline, and by wave action. As an ocean current moves parallel to the shore, it will carry away sediment. Wave action also does this, kind of similarly to currents.
A beach
A beach
On the beach in Daytona Florida and along A1A that runs along the beach