An estuary is a body of water connected to both fresh water rivers and the salty sea. As a result, estuaries are made up of brackish water, or a combination of salt water and fresh water.  Estuaries are often very good habitats for many types of aquatic creatures such as fish, crustaceans, shellfish and many types of plants, aquatic insects and microscopic plants and animals. Lake Pontchartrain is an estuary, and so is the Chesapeake Bay in Eastern North America as well as the Puget Sound in Washington State and part of Canada. People are realizing that activities even hundreds of miles away from these estuaries can have a significant impact on the health of the estuarine ecosystems, and for this reason many state governments are taking measures to protect these vital ecosystems.