or offshore bar
Submerged or partly exposed ridge of sand or coarse sediment that is built by waves offshore from a beach.
The swirling turbulence of waves breaking off a beach excavates a trough in the sandy bottom. Some of this sand is carried forward onto the beach and the rest is deposited on the offshore flank of the trough. Sand suspended in the backwash and in rip currents adds to the bar, as does some sand moving shoreward from deeper water. The bar's top is kept below still-water level by the plunge of the waves breaking over it.