Is brackish and marine water same?

Seawater contains higher amounts of dissolved salts/solids from 15,000 milligrams per liter or mg/l to over 40,000 mg/l of total dissolved solids. Water that has only 1,000 – 15,000 mg/l dissolved salts/solids is considered to be Brackish.

Marine is too broad. This is also what I am confused about. So you mean, marine has greater salinity?

Yes as the content says.

I get it now. It depends on the amount.

Yes, it is.