River mouths are the end of a river where it meets another body of water. The three most common types of river mouths are deltas, OUTLETS, and ESTUARIES. Deltas are formed when a river splits into multiple branches and deposits sediment into the body of water it is flowing into. OUTLETS are when a river flows directly into a body of water without splitting or depositing sediment. ESTUARIES are formed when a river meets the ocean and the salty ocean water mixes with the fresh river water.