Historical anecdote time!
David Richerby made an offhand comment about Archimedes of Syracuse. Archimedes had to figure out whether the king's crown was made of actual gold, but obviously he couldn't damage the crown because that would make the king angry. He had to determine the density, but you need the volume for that, and there wasn't really a way to determine the volume of an irregular object back then.
He was wondering how to do this, and at one point, he had to take a bath. Now, his servant filled the bath to the brim, and when Archimedes got into the water, some of it spilled over the edge. The legend after this goes that Archimedes saw this, jumped out of the water, and still naked, ran out onto the streets yelling "Eureka".
He had the crown weighed and asked for gold equal in mass to the weight of the crown. Then he submerged the crown and the gold into water, he saw that the gold displaced a different amount of water, despite weighing as much. This means that the volume, and thus the density of the object, was not the same, and thus that the crown was not made of solid gold. (note)
So your answer is absolutely correct: the displaced amount of water is dependent on the volume, not the weight.
(note) This is a legend. People who know more about this than me have stated that Archimedes didn't use the volume measurement, since this required measurement accuracy beyond contemporary means. Instead, the more likely method was that he tied them to a balanced scale, then submerged them, subjecting them to a buoyant force equal to the weight of the water displaced. The denser object would encounter less force and thus sink.