Final answer:
Brackish water is most commonly found in estuaries where rivers meet the sea.
Step-by-step explanation:
Brackish water is a mixture of fresh water and saltwater with a salinity level that is higher than freshwater but lower than seawater. It is commonly found in estuaries, which are areas where rivers meet the sea. Estuaries serve as a transition zone between freshwater and marine ecosystems, creating a unique habitat for various plants and animals.
Learn more about Brackish water in nature