Here's why:
* Estuaries are transitional zones where rivers meet the sea. This creates a unique environment with a mix of freshwater and saltwater.
* They are often characterized by fluctuating salinity levels as tides ebb and flow, bringing in seawater and mixing it with freshwater from rivers.
* Estuaries are incredibly diverse ecosystems supporting a wide array of plant and animal life that have adapted to these fluctuating conditions.