Answer:
When less-dense freshwater from a river flows into the estuary, it has an anti-estuarine current. Anti-estuarine currents are strongest near the surface of the water. Heated by the sun, anti-estuarine currents are much warmer than estuarine currents.
In estuaries, water level and salinity rise and fall with the tides. These features also rise and fall with the seasons. During the rainy season, rivers may flood the estuary with freshwater. During the dry season, the outflow from rivers may slow to a trickle. The estuary shrinks, and becomes much more saline.
During a storm season, storm surges and other ocean waves may flood the estuary with saltwater. Most estuaries, however, are protected from the ocean's full force. Geographical features such as reefs, islands, mud, and sand act as barriers from ocean waves and wind.
