The old word ‚€œbrack‚€? comes from the northern Low German and is a synonym for a fresh water pond or lake that has been created after it has been infected with seawater.
This is how the mixed water, which is found in river-apertures, lagoons and estuaries, came to its name.
The height of the salinity of brackish water isn‚€™t fixed, due to variabilities. Generally there are statements of about 0.05 - 3% salt concentration, with the highest percentage constituting pure seawater.
There are great waters with brackish water like the Baltic Sea, the black ocean or the Caspian Ocean. You also find higher salinity in small inland waters without any access to the sea.
The tropical mangrove swamps are typical brackish-water territories. In these territories the salinity often varies strongly and often due to the tides, evaporations or condensations.
Because of changeable salinity, almost all of the fish which appear in brackish water tolerate the high variations of salinity. Most of them originate in marine and live there at young age or wander through the zones like for instance Monodactylus argentus or Scatophagus argus, which are rather seawater fish.
These brackish-water zones and especially the Mangrove-swamps and waters are a favourite nursery for most of the residents of the ocean because of the high supply of food. The life there is fixed by the tides. Popular inhabitants are mudskippers and back on-shrimps.
Due to the salinity variations the most brackish water territories contain barely or even none of higher water plants. There are not many of the salt tolerating kinds.
But these sorts of waters contain many, also higher kinds of algaes and the tropical mangrove-woods. Mangrove is a collective term for some kinds of wood, which appear amphibian in the water of maritime shore regions.
These plants are creating tight nets of root branches which, depending on tides, lies under water or on the surface (of the sandy ground). It is a habit for many different kinds of animals.
In tropical, rarely in subtropical brackish water territories there live puffer fish of many different kinds; kinds that live there permanently or at young age which grow up there and return back to the ocean later.