Estuary's depth and temperature?

Question

in an estuary, what is the average depth and water temperature

Answer 1

There are thousands of estuaries throughout the world. Each one has it's own characteristics. I'm sure that the Bay of Fundy (Canada) has quite different parameters than those for the Mississippi River (USA).

In other words, your question doesn't have a meaningful answer.

Answer 2

An estuary is a habitat, not a climate. Estuaries occur where freshwater rivers empty into salty oceans. The climate of the mississippi estuary will be far different from the climate of an estuary for a river in alaska.