How do cells as algae and protists avoid lysis in fresh water?

Most protists lack a cell wall and would be in danger of lysis were it not for their contractile vacuole. This is a cell component with the ability to pump excess water out of the cell. Algae can afford to take in water because they are protected by their strong outer wall. When the internal pressure of the algal cell is high enough, it will oppose further inflow of water.