Over 70% of the Earth is covered with water, and we find 97% of that water in the oceans. According to the World Resources Institute, 40% of the world's population lives in the Earth's coastal regions. These regions and the people in them are affected by the ocean. Sometimes the ocean's effect is quick and dramatic, as can be seen when a tsunami or hurricane hits land. Sometimes the ocean's effect is more gentle, as can be seen in the daily ebb and flow of the tides in coastal areas.

Estuaries are found mainly on the coast. When the highly saline waters of the ocean meet fresh water that drains into the oceans, an estuary is formed. Chesapeake Bay is the largest estuary in the United States. Estuaries are unique places where life thrives! Chesapeake Bay is no exception!

Many people are interested in studying Chesapeake Bay. The High Tide program involves area high schools that are making measurements of the water in lower Chesapeake Bay in order to note how salinity, temperature and density change with different wind conditions and various freshwater discharges into the Chesapeake Bay area. High School students are collecting, analyzing, and interpreting weekly temperature and salinity profiles obtained with a CTD instrument at the Lafayette River.