What does brackish water mean?

Brackish water refers to a type of water that has a salinity level that is between fresh water and salt water. It typically occurs in areas where freshwater from rivers or streams meets and mixes with seawater, such as in estuaries or tidal zones. This slightly salty water is characterized by a measurable concentration of dissolved salts, but it is not as saline as full ocean water.

The choice indicating "slightly salty" accurately describes brackish water's properties, as it has a distinct blend of salinity that is noticeable, but not overwhelmingly salty. Other definitions, such as completely fresh, highly polluted, or pure and clear, do not capture the essential nature of brackish water, which is defined specifically by its intermediate salinity. This makes the choice referring to it as "slightly salty" the correct interpretation of brackish water.