What distinguishes a sand spit from a sand bar?

A sand spit is characterized as a landform that extends from the mainland into a body of water, typically formed by the process of longshore drift, where sediment is deposited by wave action. It usually juts out into the sea, often curving inward at its tip. This definition aligns with the characteristic of a sand spit being an "unfinished" landform, as it continues to evolve and change based on sediment depositions and erosive forces.

In contrast, a sand bar is a submerged or partially submerged accumulation of sand found offshore, often parallel to the shoreline, typically developed in deeper water than a sand spit. The distinction between the two lies primarily in the position and formation dynamics in relation to the water body. Thus, a sand spit does not close off a lagoon completely and is not a result of volcanic activity; it does not have a higher elevation than a sand bar, as both landforms are typically at similar levels relative to sea level.