Habitat
 

What is an estuary?

    A semi-enclosed body of water that has free connection with the open sea and within which seawater is diluted  measurably with fresh water derived from land drainage. (Levinton)
 
Silts and Clays - no movement with tide

Upper tide zone –plus 5 foot
Middle tide zone- 3-6 foot
Low Zone-less than 3 foot
Mud flats