Deltas form where streams transport large quantities of sediment into bodies of water such as lakes, bays, lagoons, or the ocean, creating potential reservoir facies. Depositional facies are three-dimensional rock bodies whose environmental origins can be inferred from the physical characteristics of the rock. Fluvial processes interact with the sediment reworking and redistributing properties of tidal and wave processes to varying degrees resulting in three genetic types of deltas that can be recognized based on sand distribution patterns, particularly delta front sands, and lateral and vertical facies relationships. The general area where an active stream enters the ocean or other body of water is called the delta front. Each of the three major types of deltas affects the distribution of the delta front sands, often the best reservoirs, in different ways. Fluvial-dominated deltas tend to build elongate "fingers" of delta front sands, and the general distribution of major sands tends to be perpendicular to the shoreline. The delta front sands on wave-dominated deltas tend to be reworked into numerous coastal barriers that are oriented roughly parallel to the shoreline. Tide-dominated deltas tend to have sand-choked channels and build tidal sand ridges in the delta front area which are oriented perpendicular to the shoreline.