Answer - Paramecium aka (unicellular ciliated protozoans) which can expel water thru osmosis and moves to a permeable membrane aka a layer which prevents the uni(cellular) from exploding from the fresh water and expels water from time to time. (Environment is a hypertonic) Since osmosis is water with the concentration gradient.
Reasoning - Osmosis is form of from less to high instead of high to low concentration gradient. In this case we are dealing with water which is less to high and the water is trying to get into cell. In turn thanks to that membrane which prevents it from exploding.
