Yes, many single-celled organisms, especially those living in freshwater environments, have special structures to pump excess water out. These structures are called contractile vacuoles.

Here's how they work:

* Water Movement: Freshwater has a lower solute concentration than the cell's cytoplasm, leading to water constantly diffusing into the cell due to osmosis.

* Contractile Vacuole: The contractile vacuole collects this excess water from the cytoplasm.

* Contraction: The vacuole then contracts, squeezing the water out of the cell through a pore or opening.

This process helps maintain the cell's internal water balance and prevents it from bursting due to excessive water intake.

Here are some examples of single-celled organisms that have contractile vacuoles:

* Amoeba: A common freshwater protozoan with a prominent contractile vacuole.

* Paramecium: Another freshwater protozoan with two contractile vacuoles.

* Euglena: A mixotrophic organism with a contractile vacuole that helps maintain its internal water balance.

In summary, the presence of contractile vacuoles is a crucial adaptation for single-celled organisms living in freshwater environments, allowing them to survive and thrive despite the constant influx of water.