bar

A ridge or mound of sand, gravel, or sediment deposited in a river channel or along a coast by the action of current or waves. River bars form on the inside of bends (point bars), in the middle of the channel (mid-channel bars), or at the mouths of tributaries. Coastal bars form parallel to shore, sometimes above water (barrier bars) and sometimes submerged. A bar is the river or the sea building something — accumulating material, testing a new shape.