Suppose you are in a boat on a pond and you are holding a small 10 lb weight. You drop the weight into the water. Does the water level rise, stay the same, or lower?
When the weight is in the water
it displaces the same volume of water as itself.
When it is in the boat
it causes the boat to display a volume of water with the same mass as itself.
the weight is presumably denser than water,
when you drop it in
it will displace less water and the level of water in the pond will therefore sink.