In what environments do unicellular organisms live? Why is the presence of water a prerequisite for their existence?

In unicellular organisms, the cell is both a structural unit and a whole organism. But their cell is separated from the external environment only by a membrane, on top of which, only in bacteria and plants, there is a cell wall. Therefore, for them, water is the main condition for their existence. Otherwise, the cell will die, losing water inside itself. That is why unicellular organisms live in water bodies, wet soil or inside other living creatures. Nr:
– Proteus amoeba – reservoir;
– amoeba arzella – soil;
– dysentery amoeba – human intestines.