A tidal creek, tidal channel, or estuary is the portion of a stream that is affected by ebb and flow of ocean tides, in the case that the subject stream discharges to an ocean, sea or strait. Thus this portion of the stream has variable salinity and electrical conductivity over the tidal cycle. Due to the temporal variability of water quality parameters within the tidally influenced zone, there are unique biota associated with tidal creeks, which biota are often specialised to such zones.