From Openwaterpediaopen body of water. Often called a shoal, sand bars are typically composed of sand, silt or small pebbles. A spit or sandspit is a type of sand bar or shoal.
Shoals are characteristically long and narrow (linear) and develop where a stream or ocean current promotes deposition of sand or granular material, resulting in localized shallowing (shoaling) of the water. Sand bars can appear in the ocean, sea, around a barrier island, in a lake, or in a river.
In a nautical sense, a sand bar is a shoal, similar to a reef: a shallow formation of (usually) sand that is a navigation or grounding hazard, with a depth of water of 6 fathoms (11 meters) or less. It therefore applies to a silt accumulation that shallows the entrance to the course of a river or creek.