What are the three types of estuaries?

The three types of estuaries are coastal plain estuaries, bar-built estuaries, and tectonic estuaries. Coastal plain estuaries form when sea levels rise, flooding existing river valleys. Bar-built estuaries are separated from the ocean by sandbars or barrier islands. Tectonic estuaries result from land movement, such as faults or folding, creating a depression that fills with water.