Imagine that we have a small boat floating in our bathtub. We measure the level of water. Now, we place a lead orb on board (so that it does not sink) and measure the level of water again. Now, we take this sphere and put it in water - and measure again.
The level of water will be the highest if the sphere rests on the boat - because when it sinks, its mass will not matter - only volume, and lead is denser than water.
Now, imagine that we do the same experiment wtih styrofoam instead. Is it possible to predict in which scenario more water will be displaced? When the Styrofoam is in boat or in water?