How would the contractile vacuole of a freshwater amoeba respond if the organism was placed in seawater?

The amoeba of fresh water in seawater (being this hypertonic) water will flow out of the cell, the contractile vacuole will contract more to release the water and the cell will shrink. In extreme case it will be lysed.

Explanation:

The extracellular matrix of bacteria, fungi, algae and plants is called. The cell wall or extracellular matrix is located outside the plasma membrane and is the cell compartment that mediates all cell relations with the environment. In addition, it protects the contents of the cell, gives rigidity to the cell structure and in the case of fungi and plants, the cell wall defines the structure and gives support to the tissues.

During the phenomenon known as plasmolysis, which is the separation of the living protoplast from the cell wall by a hyperosmotic effect, the physical interaction between the cell wall and the protoplast becomes evident, when this physical interaction is lost the cell is unable to respond to pathogen attack and loses its cell differentiation.

a chain link fence because there so tiny even my albino donkey can't get out