An estuary is where the salt & fresh types of this are mixed
[DOC] [TLE] Estuary definition - eWISA [PAR] Stratified estuaries are salt wedge type estuaries, in which the inflowing fresh 
water ... As small amounts of dense water are mixed in the upper layers, more 
fluid... [DOC] [TLE] vertically mixed estuary: main types of estuaries - Britannica.com [PAR] Four main types of estuaries: (A) salt-wedge estuary, (B) partially mixed estuary, (
C) ... and (D) fjord (black arrows indicate salt water and white arrows fresh).