'Greater' or 'smaller' means whatever the force is right now would change. In order to figure out how it would change, we would need to know what the cube is surrounded by right now, before it goes into the water. What I'm really trying to say is: There's not enough information in the question for us to be able to answer it.
You did not give enough information. The answer depends on the conditions before the cube is hung in water. Is it currently in air or some other fluid? Or was it resting on the bottom of a container with water in it?
